U.S. patent application number 17/469837 was filed with the patent office on 2022-04-14 for enhancements to support hst-sfn deployment scenario.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Jung Hyun BAE, Hamid SABER, Hoda SHAHMOHAMMADIAN.
Application Number | 20220116256 17/469837 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-14 |
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United States Patent
Application |
20220116256 |
Kind Code |
A1 |
SHAHMOHAMMADIAN; Hoda ; et
al. |
April 14, 2022 |
ENHANCEMENTS TO SUPPORT HST-SFN DEPLOYMENT SCENARIO
Abstract
A device, such as a UE, and a Transmit and Receive Point (TRP)
in a High-Speed Train-Single Frequency Network (HST-SFN) are
disclosed that provide network-assisted frequency-offset
compensation for the device. The device includes a receiver that
receives a first reference signal and a second reference signal
sent over a wireless network from a first TRP. The first reference
signal corresponds to a QCL RS of the second reference signal. The
device receiver determines delay-spread and average-delay
information for a path between the first TRP to the device based on
the first reference signal. The device receiver further receives a
third reference signal from a second TRP that includes
Doppler-shift and Doppler-spread information, and corresponds to a
QCL RS of a fourth reference signal transmitted from the second TRP
or corresponds to the second reference signal transmitted in a SFN
manner from the first TRP.
Inventors: |
SHAHMOHAMMADIAN; Hoda; (San
Diego, CA) ; SABER; Hamid; (San Jose, CA) ;
BAE; Jung Hyun; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Appl. No.: |
17/469837 |
Filed: |
September 8, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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63090175 |
Oct 9, 2020 |
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63130405 |
Dec 23, 2020 |
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63159443 |
Mar 10, 2021 |
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63164807 |
Mar 23, 2021 |
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International
Class: |
H04L 27/26 20060101
H04L027/26; H04L 5/00 20060101 H04L005/00; H04W 4/02 20060101
H04W004/02; H04W 72/04 20060101 H04W072/04 |
Claims
1. A device, comprising: a receiver configured to receive a first
reference signal and a second reference signal sent over a wireless
network from a first transmit and receive point (TRP), the first
reference signal corresponding to a quasi-colocation reference
signal (QCL RS) of the second reference signal, the receiver being
further configured to determine delay-spread and average-delay
information for a path between the first TRP to the device based on
the first reference signal.
2. The device of claim 1, wherein the first reference signal
comprises a Tracking Reference Signal (TRS), and the second
reference signal comprises a Physical Download Shared Channel
(PDSCH) Demodulation Reference Signal (DMRS).
3. The device of claim 1, wherein the first reference signal
comprises one of a Tracking Reference Signal (TRS) and a
Synchronization Signal Block (SSB), and the second reference signal
comprises a TRS.
4. The device of claim 1, wherein the receiver is further
configured to receive a third reference signal from a second TRP,
the third reference signal including Doppler-shift and
Doppler-spread information, and corresponds to a QCL RS of a fourth
reference signal transmitted from the second TRP or corresponds to
the second reference signal transmitted in a Single Frequency
Network (SFN) manner from the first TRP.
5. The device of claim 4, wherein the second TRP comprises a
reference TRP, the first TRP comprises a non-reference TRP, and the
first reference signal pre-compensates Doppler shift at the device
with respect to the second TRP in a High-Speed Train (HST)
scenario.
6. The device of claim 4, wherein the second reference signal is
associated with two Transmission Configuration Indicator (TCI)
states corresponding to the first reference signal and the third
reference signal.
7. The device of claim 4, wherein the receiver is further
configured to receive a Physical Download Control Channel (PDCCH)
DMRS associated with two Transmission Configuration Indicator (TCI)
states from the first TRP and the second TRP, and wherein the
receiver determines a TCI state of a PDSCH DMRS scheduled by the
PDCCH as one of the two TCI states.
8. The device of claim 4, wherein the receiver is further
configured to receive a fifth reference signal sent over the
wireless network from the first TRP and the second TRP, the fifth
reference signal comprising a two-port Phase Tracking Reference
Signal (PTRS) in which a first port of the two-port PTRS conveys
phase tracking information for the first TRP and a second port of
the two port PTRS conveys phase-tracking information for the second
TRP.
9. The device of claim 1, wherein the receiver is further
configured to receive a control message sent over the wireless
network from the first TRP to dynamically update a configuration of
one of the first reference signal and the second reference signal,
and wherein the receiver determines information based on the
control message for at least a periodicity of one of the first
reference signal and the second reference signal based on a change
of movement of the device with respect to the first TRP.
10. The device of claim 1, wherein the receiver is further
configured to receive a control message sent over the wireless
network from the first TRP, the control message dynamically
updating quasi-colocation information of one of the first reference
signal and the second reference signal, and wherein the receiver
determines information based on the control message for at least
one of Doppler shift, Doppler spread, average delay, delay spread,
and spatial receiver parameters based on a change of movement of
the device with respect to the first TRP.
11. A wireless network, comprising: a first transmit and receive
point (TRP) that includes a first transmitter configured to
transmit a first reference signal and a second reference signal
over the wireless network to a device, the first reference signal
corresponding to a quasi-colocation reference signal (QCL RS) of
the second reference signal and used by the device to determine
delay-spread and average-delay information for a path between the
first TRP to the device.
12. The wireless network of claim 11, wherein the first reference
signal comprises a Tracking Reference Signal (TRS), and the second
reference signal comprises a Physical Download Shared Channel
(PDSCH) Demodulation Reference Signal (DMRS).
13. The wireless network of claim 11, wherein the first reference
signal comprises one of a Tracking Reference Signal (TRS) and a
Synchronization Signal Block (SSB), and the second reference signal
comprises a TRS.
14. The wireless network of claim 11, further comprising a second
TRP that includes a second transmitter configured to transmit a
third reference signal and a fourth reference signal, the third
reference signal including Doppler-shift and Doppler-spread
information, and corresponds to a QCL RS of the fourth reference
signal transmitted from the second transmitter or corresponds to
the second reference signal transmitted in a Single Frequency
Network (SFN) manner from the first TRP.
15. The wireless network of claim 14, wherein the second TRP
comprises a reference TRP, the first TRP comprises a non-reference
TRP, and the first reference signal pre-compensates Doppler shift
at the device with respect to the second TRP in a High-Speed Train
(HST) scenario.
16. The wireless network of claim 14, wherein the second reference
signal is associated with two Transmission Configuration Indicator
(TCI) states corresponding to the first reference signal and the
third reference signal.
17. The wireless network of claim 14, wherein the first TRP and the
second TRP each send a Physical Download Control Channel (PDCCH)
DMRS associated with two Transmission Configuration Indicator (TCI)
states to the device from which the device determines a TCI state
of a PDSCH DMRS scheduled by the PDCCH as one of the two TCI
states.
18. The wireless network of claim 14, wherein the first TRP and the
second TRP are configured to send a fifth reference signal sent
over the wireless network to the device, the fifth reference signal
comprising a two-port Phase Tracking Reference Signal (PTRS) in
which a first port of the two-port PTRS conveys phase-tracking
information for the first TRP and a second port of the two port
PTRS conveys phase-tracking information for the second TRP.
19. The wireless network of claim 11, wherein the first TRP is
configured to send a control message sent over the wireless network
to the device to dynamically update a configuration of one of the
first reference signal and the second reference signal, and from
which the device determines information for at least a periodicity
of one of the first reference signal and the second reference
signal based on a change of movement of the device with respect to
the first TRP.
20. The device of claim 11, wherein the first TRP is further
configured to send a control message sent over the wireless network
to the device that dynamically updates quasi-colocation information
of one of the first reference signal and the second reference
signal and includes at least one of Doppler shift, Doppler spread,
average delay, delay spread, and spatial receiver parameters based
on a change of movement of the device with respect to the first
TRP.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit under 35 U.S.C.
.sctn. 119(e) of U.S. Provisional Patent Application No.
63/090,175, filed on Oct. 9, 2020, U.S. Provisional Application No.
63/130,405, filed on Dec. 23, 2020, U.S. Provisional Patent
Application No. 63/159,443, filed on Mar. 10, 2021, and U.S.
Provisional Patent Application No. 63/164,807, filed on Mar. 23,
2021, the disclosures of which are incorporated herein by reference
in their entirety.
TECHNICAL FIELD
[0002] The subject matter disclosed herein generally relates to
wireless communication systems. More particularly, the subject
matter relates to a system and a method for high-speed trains
single-frequency network (HST-SRN) transmission.
BACKGROUND
[0003] In current High-Speed Train (HST) scenarios with
Single-Frequency Network (SFN) transmission, dynamic switching
among Transmit and Receive Points (TRPs) requires additional
Tracking Reference Signal (TRS) and Channel State
Information-Reference Signal (CSI-RS) resources dedicated for SFN
transmission to derive Quasi Co-Located (QCL) properties, which
uses a large overhead of resource configuration. Additionally, in
current HST scenarios with SFN transmission, TRS and the
corresponding Demodulation Reference Signal (DMRS) ports may
experience a composite channel for a major path from each TRP,
which may necessitate a very high User Equipment (UE) complexity.
Further still, a high mobility of a UE in an HST environment may
result in a negative Doppler offset moving away from one TRP and a
positive Doppler offset moving towards another TRP and each TRP
uses independent local oscillators so the Doppler offsets may be
based on different base frequencies. Thus, in a HST-SFN scenario, a
UE may require a very high complexity to be able to accurately
estimate different Doppler shifts that are significantly different
based on a composited TRS and, as a result, may use a Wiener filter
on the estimated Doppler shifts in order to improve channel
estimation performance.
SUMMARY
[0004] An example embodiment provides a device that may include a
receiver configured to receive a first reference signal and a
second reference signal sent over a wireless network from a first
TRP in which the first reference signal corresponds to a
quasi-colocation reference signal (QCL RS) of the second reference
signal, and the receiver may be further configured to determine
delay-spread and average-delay information for a path between the
first TRP to the device based on the first reference signal. In one
embodiment, the first reference signal may be a TRS, and the second
reference signal may be a Physical Download Shared Channel (PDSCH)
DMRS. In another embodiment, the first reference signal may be one
of a TRS and a Synchronization Signal Block (SSB), and the second
reference signal may be a TRS. In yet another embodiment, the
receiver may be further configured to receive a third reference
signal from a second TRP in which the third reference signal may
include Doppler-shift and Doppler-spread information, and may
correspond to a QCL RS of a fourth reference signal transmitted
from the second TRP or may correspond to the second reference
signal transmitted in a SFN manner from the first TRP. In still
another embodiment, the second TRP may be a reference TRP, the
first TRP may be a non-reference TRP, and the first reference
signal may pre-compensate Doppler shift at the device with respect
to the second TRP in a HST scenario. In one embodiment, the second
reference signal may be associated with two Transmission
Configuration Indicator (TCI) states corresponding to the first
reference signal and the third reference signal. In another
embodiment, the receiver may be further configured to receive a
Physical Download Control Channel (PDCCH) DMRS associated with two
TCI states from the first TRP and the second TRP, and in which the
receiver may determine a TCI state of a PDSCH DMRS scheduled by the
PDCCH as one of the two TCI states. In one embodiment, the receiver
may be further configured to receive a fifth reference signal sent
over the wireless network from the first TRP and the second TRP in
which the fifth reference signal may include a two-port Phase
Tracking Reference Signal (PTRS) in which a first port of the
two-port PTRS may convey phase tracking information for the first
TRP and a second port of the two port PTRS may convey
phase-tracking information for the second TRP. In still another
embodiment, the receiver may be further configured to receive a
control message sent over the wireless network from the first TRP
to dynamically update a configuration of one of the first reference
signal and the second reference signal, and the receiver may
determine information based on the control message for at least a
periodicity of one of the first reference signal and the second
reference signal based on a change of movement of the device with
respect to the first TRP. In yet another embodiment, the receiver
may be further configured to receive a control message sent over
the wireless network from the first TRP in which the control
message may dynamically update quasi-colocation information of one
of the first reference signal and the second reference signal, and
the receiver may determine information based on the control message
for at least one of Doppler shift, Doppler spread, average delay,
delay spread, and spatial receiver parameters based on a change of
movement of the device with respect to the first TRP.
[0005] An example embodiment provides a wireless network that may
include a first TRP that may include a first transmitter configured
to transmit a first reference signal and a second reference signal
over the wireless network to a device, the first reference signal
corresponding to a QCL RS of the second reference signal and may be
used by the device to determine delay-spread and average-delay
information for a path between the first TRP to the device. In one
embodiment, the first reference signal may be a TRS, and the second
reference signal may be a PDSCH DMRS. In another embodiment, the
first reference signal may be of a TRS and a SSB, and the second
reference signal may be a TRS. In still another embodiment, the
wireless network may further include a second TRP that may include
a second transmitter configured to transmit a third reference
signal and a fourth reference signal in which the third reference
signal may include Doppler-shift and Doppler-spread information,
and may correspond to a QCL RS of the fourth reference signal
transmitted from the second transmitter or may correspond to the
second reference signal transmitted in a SFN manner from the first
TRP. In yet another embodiment, the second TRP may be a reference
TRP, the first TRP may be a non-reference TRP, and the first
reference signal may pre-compensates Doppler shift at the device
with respect to the second TRP in a HST scenario. In one
embodiment, the second reference signal may be associated with two
TCI states corresponding to the first reference signal and the
third reference signal. In another embodiment, the first TRP and
the second TRP may each send a PDCCH DMRS associated with two TCI
states to the device from which the device may determine a TCI
state of a PDSCH DMRS scheduled by the PDCCH as one of the two TCI
states. In one embodiment, the first TRP and the second TRP may be
configured to send a fifth reference signal sent over the wireless
network to the device in which the fifth reference signal may
include a two-port PTRS in which a first port of the two-port PTRS
may convey phase-tracking information for the first TRP and a
second port of the two port PTRS may convey phase-tracking
information for the second TRP. In still another embodiment, the
first TRP may be configured to send a control message sent over the
wireless network to the device to dynamically update a
configuration of one of the first reference signal and the second
reference signal, and from which the device may determine
information for at least a periodicity of one of the first
reference signal and the second reference signal based on a change
of movement of the device with respect to the first TRP. In one
embodiment, the first TRP may be further configured to send a
control message sent over the wireless network to the device that
may dynamically update quasi-colocation information of one of the
first reference signal and the second reference signal and may
include at least one of Doppler shift, Doppler spread, average
delay, delay spread, and spatial receiver parameters based on a
change of movement of the device with respect to the first TRP.
BRIEF DESCRIPTION OF THE DRAWING
[0006] In the following section, the aspects of the subject matter
disclosed herein will be described with reference to exemplary
embodiments illustrated in the figures, in which:
[0007] FIG. 1 depicts an example embodiment of a wireless
communication network according to the subject matter disclosed
herein;
[0008] FIG. 2 depicts an example embodiment of a base station
device according to the subject matter disclosed herein;
[0009] FIG. 3 depicts an example embodiment of a user equipment
according to the subject matter disclosed herein;
[0010] FIG. 4A depicts an example embodiment of a downlink slot
structure;
[0011] FIG. 4B depicts an example embodiment of an uplink slot
structure for physical uplink shared channel transmission or
physical uplink control channel transmission;
[0012] FIG. 5A depicts a block diagram of an example embodiment of
a transmitter structure using OFDM according to the subject matter
disclosed herein;
[0013] FIG. 5B depicts a block diagram of an example embodiment of
an OFDM receiver structure according to the subject matter
disclosed herein;
[0014] FIG. 6 depicts an example HST-SFN environment in which a
coherent joint transmission may occur;
[0015] FIG. 7 shows an example RS overhead over an example
bandwidth for a configuration of QCL reference RS in SFN
transmission for three TRPs;
[0016] FIG. 8 shows separate QCL RSs for three TRPs that are
sufficient for dynamic switching among the three TRPs;
[0017] FIGS. 9A-9C respectively depict three dynamic switching
scenarios in an example HST-SFN environment that includes a first
TRP, a second TRP, and a UE;
[0018] FIGS. 10A-10C depict a first aspect of a first embodiment in
which a predetermined TRP that is known to a UE is always the
reference for frequency-offset precompensation on the gNB side for
all dynamic-switching transmission cases according to the subject
matter disclosed herein;
[0019] FIGS. 11A-11C(2) depict a second aspect of the embodiment in
which a predetermined TRP that is known to a UE is always the
reference for frequency-offset precompensation on the gNB side for
all dynamic-switching transmission cases according to the subject
matter disclosed herein;
[0020] FIGS. 12A-12C respectively show
frequency-offset-compensation schemes for the three
dynamic-switching cases in which each TRP is responsible for its
own corresponding frequency-offset precompensation according to the
subject matter disclosed herein;
[0021] FIG. 13 depicts a fourth aspect of the first embodiment for
network frequency-offset precompensation that uses a three-step
process with implicit UE indication according to the subject matter
disclosed herein;
[0022] FIG. 14 depicts a fifth aspect of the first embodiment for
network frequency-offset precompensation that uses a two-step
process starting with a UL RS transmission according to the subject
matter disclosed herein;
[0023] FIGS. 15A and 15B respectively depict example embodiments
for a three-step process and a two-step process for network
frequency-offset precompensation that provides TRP-specific
frequency offset precompensation independently for each TRP
according to the subject matter disclosed herein;
[0024] FIGS. 16A and 16B respectively depict a second embodiment
for a three-step process and a two-step process for network
frequency-offset precompensation that uses a SFN-manner TRS
transmission with implicit UE indication according to the subject
matter disclosed herein;
[0025] FIGS. 17A and 17B respectively depict example embodiments
for a three-step process and a two-step process that use a
SFN-manner TRS transmission with network precompensation provided
independently for each TRP according to the subject matter
disclosed herein;
[0026] FIG. 18 depicts another aspect of the second embodiment
combines SFN and TRP-specific TRS transmission for a three-step
process according to the subject matter disclosed herein;
[0027] FIG. 19 shows yet another aspect of the second embodiment
that combines SFN and TRP-specific TRS transmission with network
precompensation of Doppler shift provided independently for each
TRP according to the subject matter disclosed herein;
[0028] FIG. 20 shows a QCL relationship of a TRS reference signal
for semi-persistent resources that may be configured through a
Medium Access Control (MAC) Control Element (CE) triggering process
according to the subject matter disclosed herein;
[0029] FIG. 21 shows reuse of a Rel-17 enhanced TCI states
activation/deactivation MAC CE structure;
[0030] FIG. 22 shows a block diagram of an example embodiment of a
UE receiver for demodulating and decoding the received data;
[0031] FIG. 23 shows an example block diagram of a UE receiver
according to the subject matter disclosed herein;
[0032] FIG. 24 shows a block diagram of an example embodiment of a
UE receiver having separate receiver chains according to the
subject matter disclosed herein;
[0033] FIGS. 25 and 26 respectively depict a single-DCI and
Multi-DCI M-TRP transmission schemes according to the subject
matter disclosed herein;
[0034] FIG. 27A depicts a scheme in which one PDCCH candidate (in a
given SS set) may be associated with both TCI states of the CORESET
according to the subject matter disclosed herein;
[0035] FIG. 27B depicts a scheme in which two sets of PDCCH
candidates (in a given SS set) may be respectively associated with
the two TCI states of the CORESET according to the subject matter
disclosed herein;
[0036] FIG. 27C depicts a scheme in which two sets of PDCCH
candidates may be associated with two corresponding SS sets in
which both SS sets may be associated with the CORESET and each SS
set may be associated with only one TCI state of the CORESET
according to the subject matter disclosed herein;
[0037] FIGS. 28A-28D depict examples of repetition schemes
disclosed herein;
[0038] FIG. 29 depicts an example of PDSCH scheduling and UE
behavior according to a Method 10 disclosed herein;
[0039] FIG. 30 depicts an example of a method 11 according to the
subject matter disclosed herein;
[0040] FIG. 31 depicts an example of a method 12 according to the
subject matter disclosed herein;
[0041] FIG. 32 depicts an example of a method 13 according to the
subject matter disclosed herein;
[0042] FIG. 33 depicts an example of an intra-slot TDM according to
the subject matter disclosed herein;
[0043] FIG. 34 depict an example of multiple consecutive chunks
with alternating TCI states with L=2 according to the subject
matter disclosed herein;
[0044] FIG. 35 depicts an example of multiple consecutive slots
with alternating TCI states based on an Inter-slot TDM case 2
according to the subject matter disclosed herein; and
[0045] FIG. 36 depicts an example of an FDM PDSCH scheme according
to the subject matter disclosed herein.
DETAILED DESCRIPTION
[0046] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the disclosure. It will be understood, however, by those skilled
in the art that the disclosed aspects may be practiced without
these specific details. In other instances, well-known methods,
procedures, components and circuits have not been described in
detail to not obscure the subject matter disclosed herein.
[0047] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment may be
included in at least one embodiment disclosed herein. Thus, the
appearances of the phrases "in one embodiment" or "in an
embodiment" or "according to one embodiment" (or other phrases
having similar import) in various places throughout this
specification may not necessarily all be referring to the same
embodiment. Furthermore, the particular features, structures or
characteristics may be combined in any suitable manner in one or
more embodiments. In this regard, as used herein, the word
"exemplary" means "serving as an example, instance, or
illustration." Any embodiment described herein as "exemplary" is
not to be construed as necessarily preferred or advantageous over
other embodiments. Additionally, the particular features,
structures, or characteristics may be combined in any suitable
manner in one or more embodiments. Also, depending on the context
of discussion herein, a singular term may include the corresponding
plural forms and a plural term may include the corresponding
singular form. Similarly, a hyphenated term (e.g.,
"two-dimensional," "pre-determined," "pixel-specific," etc.) may be
occasionally interchangeably used with a corresponding
non-hyphenated version (e.g., "two dimensional," "predetermined,"
"pixel specific," etc.), and a capitalized entry (e.g., "Counter
Clock," "Row Select," "PIXOUT," etc.) may be interchangeably used
with a corresponding non-capitalized version (e.g., "counter
clock," "row select," "pixout," etc.). Such occasional
interchangeable uses shall not be considered inconsistent with each
other.
[0048] Also, depending on the context of discussion herein, a
singular term may include the corresponding plural forms and a
plural term may include the corresponding singular form. It is
further noted that various figures (including component diagrams)
shown and discussed herein are for illustrative purpose only, and
are not drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for clarity.
Further, if considered appropriate, reference numerals have been
repeated among the figures to indicate corresponding and/or
analogous elements.
[0049] The terminology used herein is for the purpose of describing
some example embodiments only and is not intended to be limiting of
the claimed subject matter. As used herein, the singular forms "a,"
"an" and "the" are intended to include the plural forms as well,
unless the context clearly indicates otherwise. It will be further
understood that the terms "comprises" and/or "comprising," when
used in this specification, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof.
[0050] It will be understood that when an element or layer is
referred to as being on, "connected to" or "coupled to" another
element or layer, it can be directly on, connected or coupled to
the other element or layer or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly connected to" or "directly coupled to"
another element or layer, there are no intervening elements or
layers present. Like numerals refer to like elements throughout. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items.
[0051] The terms "first," "second," etc., as used herein, are used
as labels for nouns that they precede, and do not imply any type of
ordering (e.g., spatial, temporal, logical, etc.) unless explicitly
defined as such. Furthermore, the same reference numerals may be
used across two or more figures to refer to parts, components,
blocks, circuits, units, or modules having the same or similar
functionality. Such usage is, however, for simplicity of
illustration and ease of discussion only; it does not imply that
the construction or architectural details of such components or
units are the same across all embodiments or such
commonly-referenced parts/modules are the only way to implement
some of the example embodiments disclosed herein.
[0052] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
subject matter belongs. It will be further understood that terms,
such as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0053] As used herein, the term "module" refers to any combination
of software, firmware and/or hardware configured to provide the
functionality described herein in connection with a module. For
example, software may be embodied as a software package, code
and/or instruction set or instructions, and the term "hardware," as
used in any implementation described herein, may include, for
example, singly or in any combination, an assembly, hardwired
circuitry, programmable circuitry, state machine circuitry, and/or
firmware that stores instructions executed by programmable
circuitry. The modules may, collectively or individually, be
embodied as circuitry that forms part of a larger system, for
example, but not limited to, an integrated circuit (IC),
system-on-a-chip (SoC), an assembly, and so forth.
[0054] FIGS. 1-36, described below, and the various embodiments
used to illustrate the subject matter disclosed herein are only by
way of example and should not be construed in any way to limit the
scope of the subject matter disclosed herein. It should be
understood that the subject matter disclosed herein may be
implemented in any suitably arranged system or device.
[0055] At least the following documents are hereby incorporated by
reference into the present disclosure as if fully set forth herein:
3GPP TS 38.211 v15.6.0, "NR; Physical channels and modulation;"
3GPP TS 38.212 v15.6.0, "NR; Multiplexing and Channel coding;" 3GPP
TS 38.213 v15.6.0, "NR; Physical Layer Procedures for Control;"
3GPP TS 38.214 v15.6.0, "NR; Physical Layer Procedures for Data;"
3GPP TS 38.321 v15.6.0, "NR; Medium Access Control (MAC) protocol
specification;" and 3GPP TS 38.331 v15.6.0, "NR; Radio Resource
Control (RRC) Protocol Specification."
[0056] FIGS. 1-5 depict various example embodiments implemented in
wireless communications systems and use of orthogonal frequency
division multiplexing (OFDM) or orthogonal frequency division
multiple access (OFDMA) communication techniques. The descriptions
of FIGS. 1-5 are not meant to imply physical or architectural
limitations to the manner in which different embodiments may be
implemented. Different embodiments of the subject matter disclosed
herein may be implemented in any suitably-arranged communications
system.
[0057] FIG. 1 depicts an example embodiment of a wireless
communication network 100 according to the subject matter disclosed
herein. The example embodiment of the wireless network depicted in
FIG. 1 is for illustration only. Other embodiments of the wireless
network 100 may be used without departing from the principles of
the subject matter disclosed herein.
[0058] As depicted in FIG. 1, the wireless network 100 includes a
gNB 101 (e.g., base station, BS), a gNB 102, and a gNB 103. The gNB
101 may communicate with the gNB 102 and the gNB 103. The gNB 101
may also communicate with at least one network 130, such as the
internet, a proprietary Internet Protocol (IP) network, or other
data network.
[0059] The gNB 102 may provide wireless broadband access to the
network 130 for a first plurality of UEs within a coverage area 120
of the gNB 102. The first plurality of UEs may include a UE 111
that may be located in a small business (SB); a UE 112 that may be
located in an enterprise I; a UE 113 that may be located in a WiFi
hotspot (HS); a UE 114 that may be located in a first residence I;
a UE 115 that may be located in a second residence I; and a UE 116
that may be a mobile device (M), such as, but not limited to, a
cell phone, a wireless laptop, a wireless PDA, or the like. The gNB
103 may provide wireless broadband access to the network 130 for a
second plurality of UEs within a coverage area 125 of the gNB 103.
The second plurality of UEs may include the UE 115 and the UE 116.
In some embodiments, one or more of the gNBs 101-103 may
communicate with each other and with the UEs 111-116 using 5G/NR,
LTE, LTE-A, WiMAX, WiFi, and/or other wireless communication
techniques.
[0060] Depending on the network type, the term "base station" or
"BS" may refer to any component (or collection of components)
configured to provide wireless access to a network, such as a
transmit point (TP), a transmit-receive point (TRP), an enhanced
base station (eNodeB or eNB), a 5G/NR base station (gNB), a
microcell, a femtocell, a WiFi access point (AP), or other
wirelessly enabled devices. Base stations may provide wireless
access in accordance with one or more wireless communication
protocols, e.g., 5G/NR 3GPP new radio interface/access (NR), long
term evolution (LTE), LTE advanced (LTE-A), high speed packet
access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of
convenience, the terms "BS" and "TRP" are used interchangeably
herein to refer to network infrastructure components that provide
wireless access to remote terminals. Also, depending on the network
type, the term "user equipment" or "UE" may refer to any component
such as "mobile station," "subscriber station," "remote terminal,"
"wireless terminal," "receive point," or "user device." For the
sake of convenience, the terms "user equipment" and "UE" may be
used herein to refer to remote wireless equipment that wirelessly
accesses a BS, whether the UE is a mobile device (such as, but not
limited to, a mobile telephone or smartphone) or is normally
considered a stationary device (such as, but not limited to, a
desktop computer or vending machine).
[0061] Dotted lines depict approximate extents of the coverage
areas 120 and 125, which are depicted as approximately circular for
the purposes of illustration and explanation only. It should be
clearly understood that the coverage areas associated with gNBs,
such as the coverage areas 120 and 125, may have other shapes,
including irregular shapes, depending upon the configuration of the
gNBs and variations in the radio environment associated with
natural and man-made obstructions.
[0062] As described in more detail below, one or more of the UEs
111-116 may include circuitry, programming, or a combination
thereof, for efficient control signaling designed for improved
resource utilization. In certain embodiments, and one or more of
the gNBs 101-103 may include circuitry, programming, or a
combination thereof, for efficient control signaling designed for
improved resource utilization.
[0063] Although FIG. 1 depicts one example of a wireless network,
various changes may be made to FIG. 1. For example, the wireless
network 100 could include any number of gNB s and any number of UEs
in any suitable arrangement. Also, the gNB 101 may communicate
directly with any number of UEs and provide those UEs with wireless
broadband access to the network 130. Similarly, each gNB 102-103
may communicate directly with the network 130 and provide UEs with
direct wireless broadband access to the network 130. Further, the
gNBs 101, 102, and/or 103 may provide access to other or additional
external networks, such as, but not limited to, external telephone
networks or other types of data networks.
[0064] FIG. 2 depicts an example embodiment of the gNB 102
according to the subject matter disclosed herein. The embodiment of
the gNB 102 depicted in FIG. 2 is for illustration only, and the
gNBs 101 and 103 of FIG. 1 may have the same or a similar
configuration. However, gNBs come in a wide variety of
configurations, and it should be understood that FIG. 2 does not
limit the scope of the subject matter disclosed herein to any
particular implementation of a gNB.
[0065] As depicted in FIG. 2, the gNB 102 may include multiple
antennas 201a-201n, multiple radio frequency (RF) transceivers
202a-202n, receive (RX) processing circuitry 203, and transmit (TX)
processing circuitry 204. The gNB 102 may also include a
controller/processor 205, a memory 206, and/or a backhaul or
network interface 207. The TX processing circuitry 204 may include
a controller/processor that is not shown and that controls the TX
processing circuitry 204 to perform transmission-related
functionality as disclosed herein. Alternatively, the
controller/processor 205 may be configured to control the TX
processing circuitry 204 to perform transmission-related
functionality as disclosed herein.
[0066] The RF transceivers 202a-202n may receive incoming RF
signals from the antennas 201a-201n. The received RF signals may be
signals transmitted by UEs in the network 100. The RF transceivers
202a-202n may down-convert the incoming RF signals to generate IF
or baseband signals. The IF or baseband signals may be sent to the
RX processing circuitry 203, which generates processed baseband
signals by filtering, decoding, and/or digitizing the baseband or
IF signals. The RX processing circuitry 203 may transmit the
processed baseband signals to the controller/processor 255 for
further processing.
[0067] The TX processing circuitry 204 may receive analog or
digital data (such as, but not limited to, voice data, web data,
e-mail, or interactive video game data) from the
controller/processor 225. The TX processing circuitry 204 may
encode, multiplex, and/or digitize the outgoing baseband data to
generate processed baseband or IF signals. The RF transceivers
202a-202n may receive the outgoing processed baseband or IF signals
from the TX processing circuitry 204 and may up-convert the
baseband or IF signals to RF signals that are transmitted via the
antennas 201a-201n. The TX processing circuitry 204 may be
configured so that one or more beams are transmitted via the
antennas 201a-201n
[0068] The controller/processor 205 may include one or more
processors or other processing devices that may control the overall
operation of the gNB 102. For example, the controller/processor 205
may control the reception of forward channel signals and the
transmission of reverse channel signals by the RF transceivers
202a-202n, the RX processing circuitry 203, and the TX processing
circuitry 204 in accordance with well-known principles. The
controller/processor 205 may support additional functions as well,
such as more advanced wireless communication functions. For
instance, the controller/processor 205 may support beam-forming or
directional-routing operations in which outgoing/incoming signals
from/to multiple antennas 201a-201n may be weighted differently to
effectively steer the outgoing signals in a desired direction. Any
of a wide variety of other functions may be supported in the gNB
102 by the controller/processor 205.
[0069] The controller/processor 205 may also be capable of
executing programs and other processes resident in the memory 206,
such as an operating system (OS). The controller/processor 205 may
move data into or out of the memory 206, which may be coupled to
the controller/processor 205, as required by an executing process.
Part of the memory 206 may include a random-access memory (RAM),
and another part of the memory 206 may include a flash memory or
other read-only memory (ROM).
[0070] The controller/processor 205 may also be coupled to the
backhaul or network interface 207. The backhaul or network
interface 207 may allow the gNB 102 to communicate with other
devices or systems over a backhaul connection or over a network.
The interface 207 may support communications over any suitable
wired or wireless connection(s). For example, when the gNB 102 is
implemented as part of a cellular communication system (such as a
gNB supporting 5G/NR, LTE, or LTE-A), the interface 207 may allow
the gNB 102 to communicate with other gNBs over a wired or wireless
backhaul connection. When the gNB 102 is implemented as an access
point, the interface 207 may allow the gNB 102 to communicate over
a wired or wireless local area network or over a wired or wireless
connection to a larger network (such as the internet). The
interface 207 may include any suitable structure supporting
communications over a wired or wireless connection, such as an
Ethernet or an RF transceiver.
[0071] Although FIG. 2 depicts one example of gNB 102, various
changes may be made to FIG. 2. For example, the gNB 102 may include
any number of each component shown in FIG. 2. As a particular
example, an access point may include a number of interfaces 207,
and the controller/processor 205 may support routing functions to
route data between different network addresses. As another
particular example, while shown as including a single instance of
TX processing circuitry 204 and a single instance of RX processing
circuitry 203, the gNB 102 may include multiple instances of each
(such as one per RF transceiver). Also, various components in FIG.
2 may be combined, further subdivided, or omitted and additional
components may be added according to particular needs. It should be
understood that the example gNB 102 depicted in FIG. 2 may be
configured to provide any and all of the functionality of a base
station device and/or a gNB described herein.
[0072] FIG. 3 depicts an example embodiment of UE 116 according to
the subject matter disclosed herein. The embodiment of the UE 116
depicted in FIG. 3 is for illustration only, and the UEs 111-115 of
FIG. 1 could have the same or similar configuration. UEs, however,
may come in a wide variety of configurations, and FIG. 3 does not
limit a UE to be any particular implementation of a UE.
[0073] As depicted in FIG. 3, the UE 116 may include one or more
antennas 301, an RF transceiver 302, TX processing circuitry 303, a
microphone 304, and RX processing circuitry 305. The UE 116 may
also include a speaker 360, a processor 307, an input/output (I/O)
interface (IF) 308, a touchscreen 309 (or other input device), a
display 310, and a memory 311. The memory 311 may include an OS 312
and one or more applications 313. The TX processing circuitry 303
may include a controller/processor that is not shown and that may
be configured to control the TX processing circuitry 303 to perform
transmission-related functionality as disclosed herein.
Alternatively, the processor 307 may be configured to control the
TX processing circuitry 303 to perform transmission-related
functionality as disclosed herein.
[0074] The RF transceiver 310 may receive an incoming RF signal,
from the antenna 305 that has been transmitted by a gNB of the
network 100. The RF transceiver 310 may down-convert the incoming
RF signal to generate an intermediate frequency (IF) or baseband
signal. The IF or baseband signal may be sent to the RX processing
circuitry 325, which generates a processed baseband signal by
filtering, decoding, and/or digitizing the baseband or IF signal.
The RX processing circuitry 325 may transmit the processed baseband
signal to the speaker 330 (such as for voice data) or to the
processor 340 for further processing (such as for web browsing
data).
[0075] The TX processing circuitry 303 may receive analog or
digital voice data from the microphone 304 or other outgoing
baseband data (such as web data, e-mail, or interactive video game
data) from the processor 307. The TX processing circuitry 303 may
encode, multiplex, and/or digitize the outgoing baseband data to
generate a processed baseband or IF signal. The RF transceiver 302
may receive the outgoing processed baseband or IF signal from the
TX processing circuitry 303 and up-convert the baseband or IF
signal to an RF signal that is transmitted via the one or more
antennas 301. The TX processing circuitry 303 may be configured to
transmit one or more beams from the one or more antennas 301
[0076] The processor 307 may include one or more processors or
other processing devices and may execute the OS 312 stored in the
memory 311 in order to control the overall operation of the UE 116.
For example, the processor 307 may control the reception of forward
channel signals and the transmission of reverse channel signals by
the RF transceiver 302, the TX processing circuitry 303, and the RX
processing circuitry 305 in accordance with well-known principles.
In some embodiments, the processor 307 may at least one
microprocessor or microcontroller.
[0077] The processor 370 may also be capable of executing other
processes and programs resident in the memory 311, such as
processes for beam management. The processor 307 may move data into
or out of the memory 311 as required by an executing process. In
some embodiments, the processor 307 may be configured to execute
the applications 313 based on the OS 361 or in response to signals
received from gNBs or from an operator. The processor 307 may also
be coupled to the I/O interface 308, which may provide the UE 116
with the ability to connect to other devices, such as, but not
limited to, laptop computers and handheld computers. The I/O
interface 308 is the communication path between these accessories
and the processor 307.
[0078] The processor 307 may also be coupled to the touchscreen 309
and the display 310. An operator of the UE 116 may use the
touchscreen 309 to enter data into the UE 116. The display 310 may
be a liquid crystal display, light emitting diode display, or other
display capable of rendering text and/or at least limited graphics,
such as from web sites.
[0079] The memory 311 may be coupled to the processor 307. Part of
the memory 311 may include RAM and another part of the memory 311
may include a flash memory or other ROM.
[0080] Although FIG. 3 depicts one example embodiment of the UE
116, various changes may be made to FIG. 3. For example, various
components in FIG. 3 may be combined, further subdivided, or
omitted and additional components may be added according to
particular needs. As a particular example, the processor 340 may be
divided into multiple processors, such as one or more central
processing units (CPUs) and one or more graphics processing units
(GPUs). Also, while FIG. 3 depicts the UE 116 configured as a
mobile telephone or smartphone, UEs may be configured to operate as
other types of mobile or stationary devices. It should be
understood that the example UE 116 depicted in FIG. 3 may be
configured to provide any and all of the functionality of a UE
described herein.
[0081] To meet the demand for wireless data traffic that has
increased since deployment of 4G communication systems, efforts
have been made to develop an improved 5G/NR or pre-5G/NR
communication system. Therefore, the 5G/NR or pre-5G/NR
communication system may be also referred to as a "beyond 4G
network" or a "post LTE system." The 5G/NR communication system may
be considered to be implemented in higher frequency (mmWave) bands,
e.g., 28 GHz or 60 GHz bands or, in general, above 6 GHz bands, to
accomplish higher data rates or in lower frequency bands, such as
below 6 GHz, to enable robust coverage and mobility support. To
decrease propagation loss of the radio waves and increase the
transmission distance, the beamforming, massive multiple-input
multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array
antenna, an analog beam forming, large scale antenna techniques as
used in 5G/NR communication systems. Additionally, in 5G/NR
communication systems, development for system network improvement
is under way based on advanced small cells, cloud radio access
networks (RANs), ultra-dense networks, device-to-device (D2D)
communication, wireless backhaul, moving network, cooperative
communication, coordinated multi-points (CoMP), reception-end
interference cancellation and the like.
[0082] A communication system may include a downlink (DL) that
refers to transmissions from a base station or one or more
transmission points to UEs and an uplink (UL) that refers to
transmissions from UEs to a base station or to one or more
reception points.
[0083] A unit for DL signaling or for UL signaling on a cell may be
referred to as a slot and may include one or more symbols. A symbol
may also serve as an additional time unit. A frequency (or
bandwidth (BW)) unit may be referred to as a resource block (RB).
One RB may include a number of sub-carriers (SCs). For example, a
slot may have duration of 0.5 milliseconds or 1 millisecond,
include 14 symbols, and an RB may include 12 SCs with inter-SC
spacing of 30 kHz or 15 kHz, respectively. A unit of one RB in
frequency and one symbol in time may be referred to as physical RB
(PRB).
[0084] DL signals may include data signals conveying information
content, control signals conveying DL control information (DCI),
and reference signals (RS) that may also be known as pilot signals.
A gNB transmits data information or DCI through respective physical
DL shared channels (PDSCHs) or physical DL control channels
(PDCCHs). A PDSCH or a PDCCH may be transmitted over a variable
number of slot symbols including one slot symbol. For brevity, a
DCI format scheduling a PDSCH reception by a UE may be referred to
as a DL DCI format and a DCI format scheduling a PUSCH transmission
from a UE is referred to as an UL DCI format.
[0085] A gNB may transmit one or more of multiple types of RS
including channel state information RS (CSI-RS) and demodulation RS
(DM-RS). A CSI-RS may be primarily intended for UEs to perform
measurements and provide channel state information (CSI) to a gNB.
For channel measurement, non-zero power CSI-RS (NZP CSI-RS)
resources may be used. For interference measurement reports (IMRs),
CSI interference measurement (CSI-IM) resources may be used. A CSI
process may include NZP CSI-RS and CSI-IM resources.
[0086] A UE may determine CSI-RS transmission parameters through DL
control signaling or higher-layer signaling, such as radio resource
control (RRC) signaling, from a gNB. Transmission instances of a
CSI-RS may be indicated by DL control signaling or be configured by
higher layer signaling. A DM-RS may be typically transmitted only
within a BW of a respective PDCCH or PDSCH and a UE may use the
DM-RS to demodulate data or control information.
[0087] FIG. 4A depicts an example embodiment of a DL slot structure
400 according to the subject matter disclosed herein. The example
embodiment of the DL slot structure 400 depicted in FIG. 4A is for
illustration only. FIG. 4 does not limit the scope of the subject
matter disclosed herein to any particular implementation. It should
be noted that in the DL slot structure 400 described as follows,
the DCI information need not be located as depicted in FIG. 4A and
may be located elsewhere as appropriate.
[0088] As depicted in FIG. 4A, a DL slot 401 may include
N.sub.symb.sup.DL symbols 402 in which a gNB may transmit, for
example, data information, DCI, or DM-RS. A DL system BW may
include N.sub.RB.sup.DL RBs. Each RB may include N.sub.SC.sup.RB
SCs. A UE may be assigned M.sub.PDSCH RBs for a total of
M.sub.SC.sup.PDSCH=M.sub.PDSCHN.sub.SC.sup.RB SCs 403 for a PDSCH
transmission BW. A PDCCH conveying DCI may be transmitted over
control channel elements (CCEs) that are substantially spread
across the DL system BW. A first slot symbol 404 may be used by the
gNB to transmit PDCCH. A second slot symbol 405 may be used by the
gNB to transmit PDCCH or PDSCH. Remaining slot symbols 406 may be
used by the gNB to transmit PDSCH and CSI-RS. In some slots, the
gNB may also transmit synchronization signals and channels that
convey system information, such as synchronization signals and
primary broadcast channel (SS/PBCH) blocks.
[0089] UL signals may also include data signals conveying
information content, control signals conveying UL control
information (UCI), DM-RS associated with data or UCI demodulation,
sounding RS (SRS) enabling a gNB to perform UL channel measurement,
and a random access (RA) preamble enabling a UE to perform random
access. A UE may transmit data information or UCI through a
respective physical UL shared channel (PUSCH) or a physical UL
control channel (PUCCH). A PUSCH or a PUCCH may be transmitted over
a variable number of symbols in a slot including one symbol. When a
UE simultaneously transmits data information and UCI, the UE may
multiplex both in a PUSCH.
[0090] A UCI may include hybrid automatic repeat request
acknowledgement (HARQ-ACK) information, indicating correct or
incorrect detection of data transport blocks (TB s) or of code
block groups (CBGs) in a PDSCH, scheduling request (SR) indicating
whether a UE has data in the buffer to the UE, and CSI reports
enabling a gNB to select appropriate parameters for PDSCH or PDCCH
transmissions to a UE.
[0091] A CSI report from a UE may include a channel quality
indicator (CQI) informing a gNB of a largest modulation and coding
scheme (MCS) for the UE to detect a TB with a predetermined block
error rate (BLER), such as a 10% BLER, a precoding matrix indicator
(PMI) informing a gNB how to combine signals from multiple
transmitter antennas in accordance with a multiple input multiple
output (MIMO) transmission principle, a CSI-RS resource indicator
(CRI) indicating a CSI-RS resource associated with the CSI report,
and a rank indicator (RI) indicating a transmission rank for a
PDSCH.
[0092] A UL RS may include DM-RS and SRS. A DM-RS may typically be
transmitted only within a BW of a respective PUSCH or PUCCH
transmission. A gNB may use a DM-RS to demodulate information in a
respective PUSCH or PUCCH. A SRS may transmitted by a UE to provide
a gNB with an UL CSI and, for a TDD system, an SRS transmission can
also provide a PMI for DL transmission. Additionally, in order to
establish synchronization or an initial higher-layer connection
with a gNB, a UE may transmit a physical random access channel
(PRACH).
[0093] FIG. 4B depicts an example embodiment of a UL slot structure
410 for PUSCH transmission or PUCCH transmission according to the
subject matter disclosed herein. The embodiment of the UL slot
structure 410 depicted in FIG. 4B is for illustration only. FIG. 4B
does not limit the scope of the subject matter disclosed herein to
any particular implementation. It should be noted that in the UL
slot structure 410 described as follows, the UCI information need
not be located as depicted in FIG. 4B and may be located elsewhere
as appropriate.
[0094] As depicted in FIG. 4B, a slot 411 may include
N.sub.symb.sup.UL symbols 412 in which a UE transmits, for example,
data information, UCI, or DM-RS. An UL system BW may include N RBs.
Each RB may include N.sub.SC.sup.RB. A UE may be assigned
M.sub.PUXCH RBs for a total of
M.sub.SC.sup.PUXCH=M.sub.PUXCHN.sub.SC.sup.RB SCs 413 for a PUSCH
transmission BW ("X"="S") or for a PUCCH transmission BW ("X"="C").
The last one or more symbols of a slot may be used, for example, to
multiplex SRS transmissions 414 or short PUCCH transmissions from
one or more UEs.
[0095] FIG. 5A depicts a block diagram of an example embodiment of
a transmitter structure 501 using OFDM according to the subject
matter disclosed herein. The embodiment of the transmitter
structure 501 depicted in FIG. 5A is for illustration only and an
actual implementation may have the same or a similar configuration.
FIG. 5A does not limit the scope of the subject matter disclosed
herein to any particular implementation.
[0096] As depicted in FIG. 5A, information bits, such as DCI bits
or data information bits 502, may be encoded by an encoder module
503, rate matched to assigned time/frequency resources by a rate
matcher module 504 and modulated by a modulator module 505.
Subsequently, modulated encoded symbols and DM-RS or CSI-RS module
506 may be mapped to SCs by an SC mapping module 507 controlled by
a transmission bandwidth module 508. An inverse fast Fourier
transform (IFFT) may be performed by a filter module 509. A cyclic
prefix (CP) may be added to the output of the filter module 509.
The resulting signal may be filtered by common interface unit (CIU)
filter module 510 and transmitted by an RF module 511 as a
transmitted signal 512.
[0097] FIG. 5B depicts a block diagram of an example embodiment of
an OFDM receiver structure 531 according to the subject matter
disclosed herein. The embodiment of the receiver structure 531
depicted in FIG. 5B is for illustration only and an actual
implementation may have the same or a similar configuration. FIG.
5B does not limit the scope of the subject matter disclosed herein
to any particular implementation. As depicted in FIG. 5B, a
received signal 532 may be filtered by a filter module 533. A CP
removal module 534 may remove a cyclic prefix. A filter module 535
may apply a fast Fourier transform (FFT). An SC de-mapping module
536 may de-map SCs selected by BW selector module 537. Received
symbols may be demodulated by a channel estimator and a demodulator
module 538. A rate de-matcher module 539 may restore a rate
matching, and a decoder module 540 may decode the resulting bits to
provide data information bits 541. DL transmissions and UL
transmissions may be based on an orthogonal frequency division
multiplexing (OFDM) waveform that includes a variant using a DFT
preceding that is known as DFT-spread-OFDM.
[0098] As previously mentioned, an objective in the 3GPP Rel-17 SID
on RedCap NR devices is to support the same set of use cases in FR2
as in case of FR1. Beam refinement may be a key feature for FR2
operation in NR. An important issue relates to enabling a beam
refinement procedure for RedCap UEs that are in a RRC_INACTIVE
state (also referred to herein as a RRC Inactive state or an
inactive mode). Accordingly, the subject matter disclosed herein
provides a set of beam refinement procedures to enable RedCap in an
inactive mode transmission in FR2.
[0099] HST-SFN transmission is a coherent joint transmission that
employs only one Physical Downlink Control Channel (PDCCH) to
allocate one set of Physical Downlink Shared Channel (PDSCH)
resources. The same PDSCH is transmitted from multiple TRPs
simultaneously. FIG. 6 depicts an example HST-SFN environment 600
in which a coherent joint transmission may occur. In FIG. 6, a UE,
which may be traveling on a high-speed train, may receive a first
PDSCH1 from a first TRP 1 and a second PDCCH1 from a second TRP
2.
[0100] From the UE perspective, the additional downlink
transmission from TRP 2 may be interpreted as an additional
downlink delay-spread component that originated from a single TRP.
Due to the fact that each TRP may use independent local oscillators
and the UE mobility with respect to each TRP may be different than
the mobility of another UE, there may be differences in the
frequency offset at the UE. That is, a UE moving away from the
first TRP 1 and towards the second TRP 2 may experience a negative
Doppler offset moving away from the first TRP 1 and a positive
Doppler offset moving towards the second TRP 2. In a SFN-manner
transmission, both TRPs transmit the same TRS and DMRS, and as a
result the UE may perform an estimate on a composite propagation
channel. Generally, a coherent joint transmission may be viewed as
less practical because it involves an ideal transport connection
and thorough synchronization, as well as accurate channel state
information in order to ensure that the downlink transmissions sum
constructively at the UE.
TRP-Specific TRS Transmission
[0101] In a SFN transmission, an important factor to consider is
the ability of dynamic switching among TRPs. In a SFN-manner
transmission, this may involve additional SFN TRS/CSI-RS resources
dedicated for SFN transmission to derive QCL properties. As used
herein, quasi co-location means that two antenna ports are said to
be quasi co-located if properties of the channel over which a
symbol on one antenna port is conveyed can be inferred from the
channel over which a symbol on the other antenna port is conveyed.
FIG. 7 shows an example RS overhead over an example bandwidth for a
configuration of QCL reference RS in SFN transmission for three
TRPs. The abscissa in FIG. 7 is time t, and the ordinate is
frequency band f. A total of seven TRSs are used in FIG. 7 in which
three TRSs are used for TRP A, TRP B, TRP C and additional four
TRSs are used for scenarios that include TRP A+TRP B, TRP B+TRP C,
TRP A+TRP C and TRP A+TRP B+TRP C.
[0102] With multiple QCL reference RSs for the same DMRS port(s) in
which each QCL reference RS corresponds to a particular TRP
(TRP-specific), additional TRS/CSI-RS resources dedicated for SFN
transmission do not need to be configured to the UE. This may
reduce RS overhead for configuration of QCL reference RS.
[0103] FIG. 8 shows separate QCL RSs for three TRPs (i.e. TRP A,
TRP B and TRP C) that are sufficient for dynamic switching among
TRP A, TRP B, TRP C. The abscissa in FIG. 8 is time t, and the
ordinate is frequency band f. Each TRP has an independent QCL
reference RS that is frequency-division modulated (FDMed) to the
RSs of the other TRPs. Based on this, the three TRSs shown in FIG.
8 not only may be used for dynamic switching cases of TRP A, TRP B,
TRP C, but also may be used for cases of TRP A+TRP B, TRP B+TRP C,
TRP A+TRP C and TRP A+TRP B+TRP C because each TRS has an
independent QCL assumption. For example, if TRP A is used for
PDSCH, then PDSCH DMRS may be dynamically indicated to be QCLed
with the TRS from TRP A. If TRP A+TRP B are used for PDSCH, then
PDSCH DMRS may be dynamically indicated to be QCLed with both TRS
from TRP A and TRS from TRP B.
[0104] Additionally, TRS and the corresponding DMRS port(s) in a
SFN transmission may experience a composite channel representing a
major path for each TRP. In order to perform DMRS channel
estimation, a UE first estimates large-scale profiles, such as
Doppler shift, Doppler spread, average delay and delay spread. With
a single QCL reference RS, i.e., if TRS and DMRS are QCLed with a
single Transmission Configuration Indicator (TCI) state containing
a composite channel of TRPs, a UE may likely need to be of a very
high complexity to be able to accurately estimate significantly
different Doppler shifts based on a composited TRS. Such a complex
UE then may employs a Wiener filter on the estimated Doppler shifts
to improve channel-estimation performance. With multiple QCL
reference RSs for the same DMRS port(s) while each QCL reference RS
corresponds to a particular TRP (TRP-specific), a UE does not need
to estimate and track multiple Doppler shifts from a single
composited TRS. As a result, UE complexity may be significantly
decreased.
[0105] FIGS. 9A-9C respectively depict three dynamic switching
scenarios in an example HST-SFN environment 900 that includes a
first TRP 1, a second TRP 2, and a UE. FIG. 9A depicts a
dynamic-switching scenario when PDSCH is transmitted from the TRP
1. FIG. 9B depicts a dynamic-switching scenario when PDSCH is
transmitter from the TRP 2. FIG. 9C depicts a dynamic-switching
scenario when PDSCH is transmitted from both the TRP 1 and the TRP
2. Using TRP-specific (i.e., multiple QCL assumption) TRS
transmission, a total of two TRS resources, each having a separate
QCL assumption, are sufficient for dynamic switching for the three
scenarios depicted in FIGS. 9A-9B.
[0106] With TRP-specific TRS transmissions, a low-complexity UE may
accurately estimate two different Doppler shifts based on two
received TRS having separate QCL assumptions. To improve
throughput, a UE may still perform per-tap Doppler-shift channel
estimation. That is, channel coefficients may be calculated using
the estimated per-tap frequency offset and then a tap-dependent
time-domain channel interpolation.
[0107] In the following description, the functionality of the TRPs
described in the various HST-FSN scenarios and methods may be
provided by the example base station depicted in FIG. 2, and that
functionality of the EUs described in the various HST-FSN scenarios
and methods may be provided by the example UE depicted in FIG.
3.
Precompensation with TRP-Specific TRS Transmission
[0108] A first embodiment disclosed herein provides a collaboration
of network and a UE for precompensation of frequency offsets that
may be used to reduce UE complexity. That is, the network may
precompensate different frequency offsets for a UE to use to
estimate different Doppler shifts. To do so, a UE may either
explicitly report estimated Doppler shifts using a CSI framework.
Alternatively, a UE may implicitly (implicit UE indication) allow
each TRP to estimate Doppler shifts based on a UL signal
transmitted by the UE.
[0109] Doppler-shift precompensation may be provided by network
using a reference TRP for precompensation for different Doppler
shifts for both explicit reporting and implicit UE indication. The
reference TRP may be preconfigured or semi-statically indicated to
a UE. In a first aspect of the first embodiment, a particular
(predetermined) TRP may be the TRP that transmits the PDSCH in
dynamic switching between TRPs, as depicted in FIGS. 10A-10C for
the three dynamic-switching scenarios of FIGS. 9A-9C.
Alternatively, a second aspect of the first embodiment may use a
non-predetermined TRP for precompensation for different Doppler
shifts. A non-predetermined TRP that transmits a PDSCH may become
the reference TRP for a UE, as depicted in FIGS. 11A-11C for the
three dynamic-switching scenarios of FIGS. 9A-9C.
[0110] For the first aspect of the first embodiment depicted FIG.
10A-10C, a predetermined TRP (e.g., TRP 1) that is known to the UE
(e.g., may be indicated by a certain TCI state) is always the
reference for frequency-offset precompensation on the gNB side for
all dynamic-switching transmission cases.
[0111] In each of FIGS. 10A-10C, a TRP 1 is the predetermined
reference TRP. In FIG. 10A, TRP 1 sends a TRS to a UE. In FIG. 10B,
TRP 2 sends a TRS to the UE. In FIG. 5C, both TRP 1 and TRP 2 send
a TRS to the UE.
[0112] The UE experiences a doppler shift of .DELTA.f.sub.1 with
respect to TRP 1 and a doppler shift of .DELTA.f.sub.2 with respect
to TRP 2. Based on the TRS received from the referenced TRP, the UE
determines a f.sub.UE=f.sub.c+.DELTA.f, and sends a UL RS (UL
RS(f.sub.c+.DELTA.f)) to both TRP 1 and TRP 2 that conveys
f.sub.UE. In response, TRP 1 determines a
f.sub.TRP1=f.sub.UE+.DELTA.f.sub.1=f.sub.c+.DELTA.f+.DELTA.f.sub.1,
and sends a DL on f.sub.c. TRP 2 determines a
f.sub.TRP2=f.sub.UE+.DELTA.f.sub.2=f.sub.c+.DELTA.f+.DELTA.f.sub.2,
and a
.DELTA.f.sub.pre2=f.sub.TRP1-f.sub.TRP2=.DELTA.f.sub.1-.DELTA.f.sub.2,
and sends a DL that conveys f.sub.c+.DELTA.f.sub.pre2. In response
to the DL received from the TRP 1, the carrier frequency for the UE
becomes f.sub.UE=f.sub.c+.DELTA.f.sub.1.
[0113] For the second aspect of the embodiment depicted in FIGS.
11A-11C, the TRP transmitting PDSCH in each of the three
dynamic-switching cases may be the reference TRP for
frequency-offset compensation provided on the network side. Note
that for case FIG. 11C(1) and 11C(2), in which both TRP 1 and TRP 2
transmit PDSCH, either of TRPs may be considered as the reference
TRP. FIG. 11C(1) depicts when the TRP 1 is the reference TRP. FIG.
11C(2) depicts when the TRP 2 is the reference TRP.
[0114] The carrier frequency f.sub.c of received signal may
dynamically vary when handling dynamic switching among cases
depicted in FIG. 11A-11C. With a TRP-specific TRS transmission, a
multiple QCL assumption may be considered for the same DMRS ports
and a UE may be activated with a TCI codepoint having up to two TCI
states. Thus, with an assignment of one TCI state per TRP, a UE may
accordingly determine which transmission-dynamic case is being used
and address the case-specific Doppler shift for channel estimation
as long as the QCL source of Doppler shift is appropriately
indicated in the DCI. In the frequency-offset precompensation
depicted in FIGS. 10A-10C, however, the carrier frequency f.sub.c
of the received signal remains the same in the dynamic-switching
cases of FIGS. 9A-9C. Also, because the network should preconfigure
or semi-statically indicate the reference TRP to a UE, signaling
overhead for the frequency-offset-compensation depicted in FIGS.
10A-10C may be less than the signaling overhead for the
frequency-offset precompensation depicted in FIGS. 11A-11C. Based
on the lower signaling overhead, the embodiment depicted in FIGS.
10A-10C in which a predetermined TRP may be considered to be the
reference TRP for frequency-offset compensation at the gNB side may
tend to be preferred to the approaches of FIGS. 11A-11C.
[0115] In a third aspect of the first embodiment, the network may
provide precompensation for different frequency offsets per TRP
without an assignment of a reference TRP. Each TRP may be
responsible for precompensation of the frequency offset
corresponding to the path between that TRP and a UE. FIGS. 12A-12C
respectively show frequency-offset-compensation schemes for the
three dynamic-switching cases in which each TRP is responsible for
its own corresponding frequency-offset precompensation. It should
be noted that similar to the embodiment of FIGS. 10A-10C, the
carrier frequency f.sub.c of the received signal remains the same
in dynamic switching for each of the three dynamic-switching
cases.
[0116] In the current specification for a NZP-CSI-RS-ResourceSet
configured with the higher layer parameter trs-Info, a UE shall
assume the antenna port is the same as the same port index of the
configured NZP CSI-RS resources in the NZP-CSI-RS-ResourceSet.
Thus, all of the different TRS resources in a set may be
represented as one resource.
[0117] The subject matter disclosed herein provides that
TRP-specific TRS reference signals may be transmitted from two TRPs
configured as one set because this aspect is applicable to all
scenarios described in connection with FIGS. 10A-10C, 11A-11C and
12-12C because QCL information of NZP CSI-RS is configured at the
resource level, which may reduce the overhead of a TRS set
configuration. It should be noted that the antenna port with the
same port index of the configured TRS resources in the set may be
the same only if the resources have the same TCI state.
[0118] Each NZP-CSI-Resource may be configured with a frequency
domain allocation bit string in resource mapping in the 3GPP
Specification 38.331, as shown below. Among all possible mappings,
only row 1 may be used for TRS reference signal as row 1 has a high
density of three REs per an RB that provides for measurement
accuracy to track time and frequency offsets. The four-bit string
of row 1 that may have only a single bit set to "1" may be used to
indicate the first RE in frequency-domain allocation.
TABLE-US-00001 CSI-RS-ResourceMapping Information Element
CSI-RS-ResourceMapping ::= SEQUENCE { frequencyDomainAllocation
CHOICE { row1 BIT STRING (SIZE (4)), row2 BIT STRING (SIZE (12)),
row4 BIT STRING (SIZE (3)), other BIT STRING (SIZE (6)) }, ...
firstOFDMSymbolInTimeDomain INTEGER (0..13),
firstOFDMSymbolInTimeDomain2 INTEGER (2..12) OPTIONAL, ...
indicates data missing or illegible when filed
[0119] The TRS resource set may be configured so that
CSI-RS-ResourceMapping of TRS reference signals (i.e., NZP CSI-RS
Resources) transmitted from two TRPs use different bit strings to
have non-overlapping frequency-domain RE allocation. The TRS
transmission from two TRPs may be simultaneous (i.e., with same
firstOFDMSymbolInTimeDomain configuration) or with same symbol
offset (i.e., with different firstOFDMSymbolInTimeDomain
configuration). It should be noted that for aperiodic TRS reference
signals, transmission from two TRPs are at the same slot because
the aperidicTriggeringOffset parameter is configured per set and
not for each resource separately. The aperidicTriggeringOffset
parameter indicates a time offset between the slot in which a UE
receives the aperiodic trigger and the slot during which the
resource set is transmitted.
[0120] Performance in an HST scenario might be particularly
sensitive to Doppler measurement errors based on the high
mobilities and corresponding high Doppler shifts. In order to have
an accurate estimate of a Doppler shift in the vicinity of TRPs, a
frequent rate of transmission of TRS may be used. A lower rate of
TRS may, however, be sufficient in areas relatively far from TRPs.
Thus, a MAC CE may dynamically update the TRS transmission period
for an HST deployment scenario to avoid RRC reconfiguration
overhead.
[0121] Similarly, when a network precompensates frequency offset,
accuracy of Doppler shift estimation at a gNB may be affected by
rate of UL RS transmission. A frequent rate of a Sounding Reference
Signal (SRS) transmission may be used in the vicinity of TRPs while
a lower rate of SRS transmission may be sufficient in areas
relatively far from TRPs. A MAC CE may be used to dynamically
update the UL RS transmission period for HST deployment
scenario.
Network Frequency Offset Precompensation with Explicit UE
Reporting
[0122] One embodiment of network frequency-offset precompensation
provides explicit UE reporting. For this embodiment, a UE may
explicitly report the different Doppler shifts measured for each
TRP as part of a CSI reporting to a gNB. With a TPR-manner TRS/CSI
RS transmission, large-scale profile measurement, including Doppler
shift and Doppler spread, may be performed independently for each
TRP. It is, however, noted that this additional reporting of
Doppler shift may increase reporting overhead and may also include
a UE estimation error and/or feedback latency.
[0123] The current specification framework for CSI report
triggering and transmission may be used for explicit UE reporting.
One approach may be to have the network utilize channel measurement
variable to calculate Doppler shift. Another solution may be
introduction of a new report quantity for Doppler shift in
CSI-ReportConfig. Note that TRS is a CSI reference-signal resource
set with a specific configuration to maximize tracking performance.
The trs-info flag within the NZP-CSI-RS-ResourceSet parameter
structure indicates that the CSI RS resource set is being used as a
TRS. An example of specification modification to address explicit
UE reporting of Doppler shift(s) per TRP (trs-dopplershift) may be
as follows.
TABLE-US-00002 CSI-ReportConfig information element
CSI-ReportConfig ::= SEQUENCE { ... reportQuantity CHOICE { none
NULL, cri-RI-PMI-CQI NULL, cri-RI-il NULL, cri-RI-il-CQI SEQUENCE {
pdsch-BundleSizeForCSI ENUMERATED {n2, n4} OPTIONAL }, cri-RI-CQI
NULL, cri-RSRP NULL, ssb-Index-RSRP NULL, cri-RI-LI-PMI-CQI NULL,
trs-doppleshift NULL }, ... ... indicates data missing or illegible
when filed
[0124] As the current specification explicitly prevents TRS to be
included in CSI reporting, introduction of a new report quantity
for Doppler shift in CSI-ReportConfig may involve removing such a
restriction. That is, a UE may be configured with a
CSI-ReportConfig that is linked to a CSI-ResourceConfig containing
an NZP-CSI-RS-ResourceSet configured with trs-Info. Also, a UE may
be configured with a CSI-ReportConfig with the higher layer
parameter reportQuantity set to other than `none` for NZP CSI-RS
resource set configured with trs-Info.
Network Frequency Offset Precompensation with Implicit UE
Indication
[0125] Another embodiment of network frequency-offset
precompensation provides implicit UE indication. Note that TRS
transmission in these schemes are TRP-specific (i.e., TRS.sub.TRP
as shown in FIGS. 13-15).
[0126] FIG. 13 depicts a fourth aspect of the first embodiment for
network frequency-offset precompensation that uses a three-step
process with implicit UE indication according to the subject matter
disclosed herein. The process starts at 1301 with a TRS
transmission. A set of TRP-specific TRS (i.e., with independent QCL
assumption) may be transmitted from two TRPs 1 and 2. A UE
estimates the carrier frequency and two Doppler shifts based on the
received TRS set. At 1302, the UE transmits the uplink reference
signal (e.g., SRS) to the two TRPs modulated with the estimated
carrier frequency based on the received TRS set. At 1303, the
network estimates frequency offset difference of received UL RS
(i.e., SRS) at the two TRPs and precompensate the frequency offset
difference .DELTA.f.sub.pre for downlink transmission (i.e., TRS,
DMRS, PDSCH) from the non-reference TRP.
[0127] The initial set of TRS transmission at 1301 in FIG. 13 may
be transmitted for the purpose of a frequency offset estimation at
a UE. It may also be for the purpose of a QCL RS for the UL RS
(e.g., SRS) transmission at 1302. The TRS transmission may only
happen once as an aperiodic transmission for this aspect of the
first embodiment and may not be used for every DMRS and PDSCH
transmission. Additionally, in the current specification, there may
be no obligation for a UE to use TRS for carrier-frequency
estimation and the UE may use any other DL RS to maintain a
frequency loop. That is, the main process for precompensation of
the different Doppler shifts by the network for downlink
transmission may include periodic transmission of UL RS (at 1302)
and TRS (at 1303) in FIG. 13.
[0128] FIG. 14 depicts a fifth aspect of the first embodiment for
network frequency-offset precompensation that uses a two-step
process starting with a UL RS transmission according to the subject
matter disclosed herein. The two-step process is similar to 1302
and 1303 in FIG. 13.
[0129] It should be noted that a frequency-offset difference (i.e.,
.DELTA.f.sub.pre) precompensation at a gNB for downlink
transmission may be used for either for the fourth aspect of the
first embodiment depicted in FIG. 13 for all TRS, DMRS and PDSCH,
or the fifth aspect of the first embodiment depicted in FIG. 14 for
only DMRS and PDSCH, but not for TRS transmission.
[0130] In the fourth and fifth aspects of the first embodiment, TRS
overhead for dynamic-switching transmission may be reduced. A
traditional QCL rule for delay-related large-scale profile,
however, may not be held because TRSs may be transmitted in
TRP-specific while DMRS and PDSCH may be transmitted in a SFN
manner. To address this, it may be noted that a Rel-17 UE may be
activated using a TCI codepoint having two TCI states. In the
current specification, the two activated TCI states correspond to
different DMRS ports. Herein, a UE may associate the PDSCH DMRS
port(s) with both TCIs simultaneously (i.e., one TCI state per each
TRP). That is, multiple-QCL assumptions may be considered for the
same DMRS port(s). The DMRS antenna port(s) associated with each
TRP may be configured to be QCLed with the TRS transmitted from
that TRP.
[0131] For a Doppler-shift-related large-scale profile, if
frequency offset is precompensated for by the TRS as well as DMRS
and PDSCH (i.e., the fourth aspect), there would not be any issue
for a QCL rule or UE-side frequency offset tracking based on the
received TRS. There is no QCL rule break for Doppler shift
information because the QCL RS for the DMRS and PDSCH is the TRS on
the second TRS transmission. Additionally, for a second TRS
transmission precompensated for frequency offset, there would not
be any issue for a UE to estimate and compensate the frequency
offset of DMRS and PDSCH according to received TRS.
[0132] If frequency offset is not precompensated for a TRS, but for
DMRS and PDSCH (i.e., the fifth aspect), the QCL rule for Doppler
shift breaks for the DMRS and PDSCH transmission from the
non-reference TRP. A UE may estimate and precompensate the
frequency offset based on the received TRS. Not having the TRS
precompensated, but having DMRS and PDSCH precompensated for
frequency offset, a UE may estimate the frequency offset based on
the TRS, and may apply the estimate for received DMRS and PDSCH
that are already compensated by the network. To address a QCL break
issue in the first embodiment, a new QCL type may be used for TRS
transmitted from the non-reference TRP that only includes a
delay-related large-scale profile (i.e., delay spread and average
delay). That is, the QCL RS for the PDSCH DMRS may be the TRS
transmitted from the reference TRP with QCL type B and the second
TRS transmission from the non-reference TRP may only be used to
extract the delay-spread and average-delay information for the path
from a non-reference TRP to a UE. Also, to solve the
frequency-offset tracking issue based on TRS on the UE side, if the
TRS transmission is TRP-specific, a gNB may indicate to the UE to
track the frequency offset only based on received TRS from the
reference TRP (e.g., pre-configured or semi-statically indicated
with a certain TCI state). In the fourth and fifth aspects of the
first embodiment respectively depicted in FIGS. 13 and 14, the
network precompensates the difference of frequency Doppler shifts
based on one TRP as the reference TRP. As previously described, the
network may precompensate Doppler shifts separately for each TRP.
The approaches and explanations of FIGS. 13 and 14 may be extended
and applied to a situation in which Doppler frequency shift is
precompensated for each TRP independently by network.
[0133] FIGS. 15A and 15B respectively depict example embodiments
for a three-step process and a two-step process for network
frequency-offset precompensation that provides TRP-specific
frequency offset precompensation independently for each TRP
according to the subject matter disclosed herein. It should however
be noted that only the three-step-process embodiment of FIG. 15A
may be considered for a situation in which frequency offset is
precompensated for all downlink transmission (i.e., TRS, DMRS and
PDSCH). With the two-step process, an uncompensated TRS may not be
considered as the QCL RS of PDSCH DMRS due to a QCL rule break
while channel estimation still involves a QCL RS of PDSCH DMRS to
extract a Doppler-shift-related large-scale profile.
SFN-Manner TRS Transmission
[0134] A SFN-manner TRS transmission may involve a high-complexity
UE to accurately estimate significantly different Doppler shifts
based on a composited TRS. If the network precompensates the
different Doppler shifts from two TRPs, a high-complexity UE may
not be needed for channel estimation and PDSCH demodulation.
[0135] In the embodiments disclosed herein using a three-step or a
two-step process for network frequency offset precompensation with
TRP-specific TRS transmission, the value of estimated carrier
frequency at a UE may not need to be accurate because the estimated
carrier frequency is only used for an uplink RS transmission to two
TRPs and the network may precompensate the Doppler shift difference
of the two TRPs.
[0136] A second embodiment disclosed herein involves a UE and
network collaboration with a SFN-manner TRS transmission (i.e.,
TRS.sub.SFN). It may be noted that using a SFN-manner TRS
transmission with network frequency-offset precompensation may
reduce UE complexity with backward compatibility with a traditional
HST-SFN deployment scenario, however, a high TRS overhead may still
be involved.
Network Frequency Offset Precompensation with Implicit UE
Indication
[0137] FIGS. 16A and 16B respectively depict a second embodiment
for a three-step process and a two-step process for network
frequency-offset precompensation that uses a SFN-manner TRS
transmission with implicit UE indication according to the subject
matter disclosed herein. In the embodiment depicted in FIG. 16A, a
set of TRS may be transmitted from two TRPs at 1601. At 1602, a UE
transmits an uplink reference signal to the two TRPs. At 1603, the
network estimates a frequency offset difference at the two TRPs and
precompensates the Doppler shift difference for downlink
transmission for the non-reference TRP. For this embodiment, the
TRS transmission at both 1601 and 1603 may be based on a
SFN-manner. The embodiment depicted in FIG. 16B is similar to the
embodiment of FIG. 16A, but starts at 1602 because the first step
at 1601 is not used for a two-step process. It may be noted that
only the embodiment of FIG. 16A involves a frequency offset may be
precompensated for the TRS as well as DMRS and PDSCH because
channel estimation involves the QCL source of PDSCH DMRS for
Doppler shift and a SFN-manner TRS may not be QCL RS in the
embodiment of FIG. 16B because of a QCL rule break unless an
additional resource is provided for that a QCL rule break, which
may not be practical.
[0138] For a SFN-manner TRS transmission in FIG. 16A, a UE
estimates the UL carrier frequency for a SRS transmission based on
a received composited TRS. A high-complexity UE may track multiple
Doppler shifts from a single composited TRS and there may be a high
likelihood that the UE may estimate an incorrect frequency offset
at 1602. However, the value of estimated carrier frequency at the
UE does not involve any significant operational error because the
estimated carrier frequency is only used for an uplink RS
transmission to two TRPs so that the network may estimate and
compensate frequency offset difference of the two TRPs.
[0139] For delay-related large-scale profile using the embodiments
of FIGS. 16A and 16B, there is no QCL rule break considering the
QCL RS for the DMRS and PDSCH is the TRS on the second TRS
transmission in which both TRS and the corresponding DMRS port(s)
experience a composite channel considering a major path for each
TRP. The SFN-manner transmission may, however, involve a high TRS
overhead in order to derive the QCL properties of dynamic switching
among TRPs.
[0140] Frequency offset is always compensated for the TRS as well
as DMRS and PDSCH for Doppler-shift related large-scale profile in
the embodiments of FIGS. 16A and 16B, so there would not be any
issue for QCL rule on Doppler shift information and also for
UE-side frequency offset tracking and compensation based on
received TRS.
[0141] FIGS. 17A and 17B respectively depict example embodiments
for a three-step process and a two-step process that use a
SFN-manner TRS transmission with network precompensation provided
independently for each TRP according to the subject matter
disclosed herein. The explanations provided for FIGS. 16A and 16B
are applicable to the embodiments of FIGS. 17A and 17B.
[0142] Another aspect of the second embodiment combines SFN and
TRP-specific TRS transmission for a three-step process, as shown in
FIG. 18. At 1801, a TRS transmission is made in a SFN manner. At
1802, the UE sends an UL RS. At 1803, a second TRS transmission is
sent that is TRP-specific. The TRP-specific transmission provides
an independent delay-spread information estimation and TRS overhead
reduction for dynamic switching. Also, similar to a TRP-specific
TRS transmission, frequency-offset difference precompensation at a
gNB for downlink transmission may be used either for all TRS, DMRS
and PDSCH, or only for DMRS and PDSCH and not TRS transmission.
[0143] The second set of TRS may be considered as the QCL RS for
the DMRS and PDSCH. With TRP-specific TRS, a traditional QCL rule
for delay-related large-scale profile may not hold because TRSs are
transmitted as TRP-specific while DMRS and PDSCH are transmitted in
an SFN manner. To address this issue, it is noted that a Rel-17 UE
may be activated with a TCI codepoint having two TCIs. In the
current specification, the two activated TCI states correspond to
different DMRS ports. Here, the approach is that a UE may associate
the PDSCH DMRS port(s) with both TCIs simultaneously (i.e., one TCI
state per each TRP). That is, multiple-QCL assumptions may be
considered for the same DMRS ports. The DMRS antenna port
associated with each TRP may be configured to be QCL with the TRS
transmitted from that TRP.
[0144] In a dynamic-switching scenario of FIG. 9A for a
Doppler-shift related large-scale profile using the approach of
FIG. 18, there would not be any issue for QCL rule on Doppler-shift
information and also for a UE-side frequency offset tracking and
compensation based on received TRS. The QCL RS of the PDSCH DMRS
is, however, the second TRS transmitted from the reference TRP with
QCL type B and a new QCL type may be introduced for TRS of a
non-reference TRP that only contains a delay-related large-scale
profile. Also, a gNB should indicate to a UE that only TRS of the
reference TRP may be considered as the QCL RS for Doppler
shift-related large-scale profile.
[0145] FIG. 19 shows another aspect of the second embodiment that
combines SFN and TRP-specific TRS transmission with network
precompensation of Doppler shift provided independently for each
TRP according to the subject matter disclosed herein. The
explanation of aspect of the second embodiment depicted in FIG. 18
is applicable to the aspect of the second embodiment depicted in
FIG. 19, except that aspect depicted in FIG. 19 may only be
considered for a situation in which frequency offset is
precompensated for all downlink transmissions (i.e., TRS, DMRS and
PDSCH) based on a QCL rule-breaking issue.
[0146] Table 1 sets forth a summary of some features and
characteristics associated with the first and second
embodiments.
TABLE-US-00003 TABLE 1 TRP- Combined SFN-TRP specific SFN-manner
specific QCL rule break for TRS overhead, QCL rule break for delay,
spread and UE complexity. delay, spread and average delay average
delay information. information. TRS overhead reduction, No QCL rule
break, backward compatibility, less UE complexity. backward TRS
overhead reduction, compatibility. less UE complexity.
QCL Assumption of TRS as Target RS
[0147] QCL relationship information may help a UE with channel
estimation, frequency offset estimation and synchronization
processes. The QCL relationship of a TRS reference signal may be
configured per resource through NZP-CSI-RS-Resource for periodic
resources, as shown below. For semi-persistent resources, the QCL
relationship of a TRS reference signal may be configured through a
Medium Access Control (MAC) Control Element (CE) triggering
process, as shown in FIG. 20. For aperiodic resources, the QCL
relationship of a TRS reference signal may be configured through a
DCI triggering process for aperiodic resources, as shown below.
TABLE-US-00004 NZP-CSI-RS-Resource information element a) Periodic
NZP-CSI-RS-Resource ::= SEQUENCE { ... qci-InfoPeriodicCSI-RS
TCI-StateID OPTIONAL, ... } indicates data missing or illegible
when filed
TABLE-US-00005 b) Aperiodic CSI-AperiodicTriggerStateList
information element CSI-AperiodicTriggerStateList ::= SEQUENCE
(SIZE (1..maxNrOfCSI-AperiodicTriggers)) OP CSI-
AperiodicTriggerState CSI-AperiodicTriggerState ::= SEQUENCE {
associatedReportConfigInfoList SEQUENCE
(SIZE(1..macNrofReportConfigPerAperiodicTrigger)) OF
CSI-AssociatedReportConfigInfo, ... }
CSI-AssociatedReportConfigInfo ::= SEQUENCE { reportConfigId
CSI-ReportConfigId, resourceForChannel CHOICE { nzp-CSI-RS SEQUENCE
{ resourceSet INTEGER (1..maxNrofNZP-CSI-RS-ResourceSetsPerConfig),
qcl-info SEQUENCE (SIZE (1..maxNrofAP-CSI-RS-ResourcesPerSet)) OF
TCI-StateId Optional }, ... } indicates data missing or illegible
when filed
[0148] For a semi-persistent CSI-RS resource set
activation/deactivation by MAC CE (FIG. 20), a MAC CE structure
indicates the index of NZP-CSI-RS-ResourceSet contains
semi-persistent NZP CSI-RS resources as well as TCI-StateIds that
may be used as a QCL source for the resources within the indicated
resource set. For aperiodic CSI-RS, CSI request field in DCI format
0_1 may take up to 6 bits (determined by a higher layer parameter
reportTriggerSize within CSI-MeasConfig) that selects one among all
trigger states. The TCI state and QCL information may be configured
inside CSI-AssociatedReportConfiglnfo for each nzp-CSI-RS.
[0149] The large-scale radio-channel characteristics, such as
Doppler shift, Doppler spread, average delay and delay spread, may
be common across different antenna ports. A QCL-type relationship
may be introduced to support a UE for channel estimation,
frequency-offset estimation and synchronization processes in
reception of PDCCH and PDSCH. In the current specification, four
different types of QCL relationship are defined to indicate channel
large-scale characteristics across a set of QCL antenna ports, as
below:
QCL type A: {Doppler shift, Doppler spread, average delay, delay
spread}, QCL type B: {Doppler shift, Doppler spread}, QCL Type C:
{Doppler shift, average delay}, and QCL Type D: {spatial receiver
parameters}.
[0150] For all of the embodiments disclosed herein, a QCL reference
signal for TRS transmission at a first step (applicable to a
three-step process) may be a specific Synchronization
Signal/Physical Broadcast Channel (SS/PBCH) block or any other CSI
reference signal with QCL type A covering QCL relation for both
delay and Doppler-shift related large-scale profile. A QCL type D
reference signal for TRS transmission at the first step may used as
a corresponding TRP-specific SS/PBCH block.
[0151] For a second TRS transmission (at the third step for a
three-step process or at the second step for a two-step process),
however, the situation for TCI state and QCL information
configuration may be different. The QCL reference signal of the
second transmitted TRS may be defined differently depending on the
fact that that the network precompensates frequency offset for all
TRS, DMRS and PDSCH, or that the network precompensates frequency
offset only for DMRS and PDSCH and not TRS. A QCL type D reference
signal for the second TRS transmission, in both types of cases (a
three-step or a two-step processes) may be a corresponding
TRP-specific SS/PBCH block or a first TRS transmitted from the
corresponding TRP.
[0152] With a three-step process, the QCL RS of the second TRS
transmitted from the reference TRP may be the first TRS transmitted
from the reference TRP. Alternatively, the QCL RS of the first TRS
transmitted from the reference TRP with QCL type A (i.e., all
Doppler shift, Doppler spread, average delay and delay-spread
information) may be the first TRS transmitted from the reference
TRP. Also, for a delay-related large-scale profile, the QCL RS for
the second TRS transmitted from a non-reference TRP may be the
first TRS transmitted from that TRP or the QCL RS of the first TRS
transmitted from that TRP with a new QCL type definition that only
includes average delay and delay-spread information. For a
Doppler-shift-related large-scale profile, the QCL RS for the
second TRS transmitted from a non-reference TRP may be the
first/second TRS transmitted from the reference TRP or the QCL RS
of the first/second TRS transmitted from the reference TRP with QCL
type B.
[0153] As there may be no TRS transmission at the first step with
two-step process, the QCL RS of the TRS transmitted from the
reference TRP may be a specific SS/PBCH block or any other CSI
reference signal with QCL type A, while the QCL RS of the TRS
transmitted from the non-reference TRP may be a specific SS/PBCH
block or any other CSI reference signal with new QCL type for delay
spread and average delay information and for Doppler shift and
Doppler-spread information. The QCL RS of the TRS may be TRS
transmitted from the reference TRP or the QCL RS of the TRS
transmitted from the reference TRP with QCL type B.
[0154] In the current specification, each TCI-State contains a QCL
relationship for one or two downlink reference signals with two
different QCL types. For the second TRS transmission from a
non-reference TRP in a three-step process and the TRS transmission
in a two-step process, in addition to QCL type D, another two
different QCL types may be used (i.e., a new QCL type for
delay-related large-scale profile and a QCL type B for Doppler
shift-related large-scale profile). To address this issue, the
specification may be modified to allow up to three different QCL
types as well as DL reference signals configuration in each TCI
state.
[0155] With a three-step process, the QCL RS of the second TRS
transmitted from each TRP may be the first TRS transmitted from
that TRP, or may be the QCL RS of the first TRS transmitted from
that TRP with QCL type A. With a two-step process, the QCL RS of
the TRS transmitted from each TRP may be a specific SS/PBCH block
or any other CSI reference signal with QCL type A.
[0156] Additionally, with a three-step network precompensation,
there may be two different situations to consider. First, both TRS
transmissions are from the same resource set, and second, two
different TRS resource sets may be configured for first and second
TRS transmission.
[0157] A first situation involves a QCL information update for the
second TRS transmission as the network precompensation of frequency
offset breaks the previously configured QCL relation information of
TRS resources. In this situation, a MAC CE may be used to update
the QCL information of the TRS resources in the set similar to the
current MAC CE structure for activation/deactivation of
semi-persistent CSI-RS as shown in FIG. 20. Alternatively, the
network may only configure QCL type D, a new QCL type that only
includes delay-related large-scale profile information, and the
corresponding reference signals in TCI state of TRS as the source
RS. The RS of QCL type B for TRS as source RS may be the TRS
itself.
[0158] Additionally, the first scenario assumption may be
compatible with no further impact because the second TRS
transmission is not precompensated by the network. It may be noted
that in this scenario, the QCL type D reference signal may be the
corresponding TRP-specific SS/PBCH block.
[0159] For the second scenario assumption, the QCL RS of the second
TRS transmitted from the reference TRP may be the first TRS
transmitted from that TRP or the QCL RS of the first TRS
transmitted from that TRP with QCL type A. The QCL RS for the
second TRS transmitted from the non-reference TRP may be the first
TRS transmitted from that TRP or the QCL RS of the first TRS
transmitted from that TRP with QCL type A. While for a
delay-related large-scale profile, the QCL RS for the second TRS
transmitted from the non-reference TRP may be the first TRS
transmitted from that TRP. Alternatively, the QCL RS of the first
TRS transmitted from that TRP may include a new QCL type that only
includes average delay and delay-spread information. For a
Doppler-shift related large-scale profile, the QCL RS for the
second TRS transmitted from the non-reference TRP may be the
first/second TRS transmitted from the reference TRP. Alternatively,
the QCL RS of the first/second TRS may be transmitted from the
reference TRP with QCL type B. It is noted that in the second
scenario, the QCL type D reference signal may be the corresponding
TRP-specific SS/PBCH block, or may be the first TRS transmitted
from the corresponding TRP.
[0160] With a frequency-offset precompensated TRS, the second TRS
transmitted from non-reference TRP should be configured with a
dynamic carrier frequency as the Doppler frequency shift changes
over time as a UE moves or changes speed. As different TRS
transmission occasions would have different precompensation status,
a frequency tracking mechanism at a UE may suffer from an
averaging/accumulation issue. This issue may be addressed with a
dynamic QCL information update for the second TRS transmission. The
dynamic update, as previously mentioned, may be used based on the
fact that the network precompensation of frequency offset breaks
the previously configured QCL relation info of TRS resources. With
a dynamic update of QCL source RS, TCI state changes for
precompensated TRS may provide an indication to a UE not to do
averaging/accumulation for the TRS transmission occasions.
[0161] An alternative solution may be that a gNB may indicate to a
UE to only use transmitted TRS from reference TRP for carrier
frequency estimation to maintain averaging/accumulation structure
of frequency loop. The reference TRP may be realized either by QCL
indication in DCI scheduling PDSCH or
pre-configured/semi-statically indicated to a UE.
TRP-Specific TRS and DMRS Transmission
[0162] With a TRP-specific TRS transmission, a UE may be able to
estimate two significantly different large-scale profiles
especially for Doppler-shift based on the two separate TRSs. A UE,
however, may still include a high complexity for per-tap Doppler
shifts channel estimation. That is, the channel coefficients may be
calculated using the estimated per tap frequency offset and then a
tap-dependent time-domain channel interpolation may be performed to
improve the channel-estimation performance and throughput. An
alternative solution to improve DMRS channel estimation performance
with a less complex UE may be that each TRP may use an independent
DMRS port in PDSCH.
[0163] With a TRP-specific TRS and DMRS transmission, a UE may
estimate the propagation channel for each TRP orthogonally based on
each DMRS antenna port mapped to each TRP. The UE then may
reconstruct a composite SFN channel by combining of the estimated
channels from different TRPs. This may reduce complexity of a UE
channel estimation algorithm having improved performance. Hence,
network collaboration for precompensation of frequency Doppler
shifts may no longer be used and a UE may take care of
significantly different frequency offsets from two TRPs with low
complexity.
[0164] An enhanced Rel-17 MAC-CE may activate two TCI states per a
TCI code point. That may enable a UE to associate DMRS with both
TCIs simultaneously. To address this, one solution may be using a
comb-like TCI state allocation in which even-comb REs may be
assigned to the first TCI state and odd-comb REs may be assigned to
the second TCI state. For a DMRS type 1, this may mean that each
TCI state may be allocated to one CDM group. Hence, generalizing
this solution, each CDM group may be assigned to one TCI state at
least for DMRS type 1.
[0165] Another solution may be to allocate the TCI state in TD-OCC
manner in which two orthogonal DMRS ports in one CDM group may be
assigned to two different TCI states. All of the embodiments
disclosed herein may allow a UE to use an orthogonal channel
estimation algorithm.
Rel-16 and Rel-17 Schemes Dynamic Switching
[0166] For a TRP-based precompensation, the same DMRS port(s) may
associate with up to two TCI states. This may be interpreted as an
implicit indication/switching between a Rel-17 SFN-based
frequency-offset precompensation technique and a single TRP or
Rel-15 SFN frequency-offset precompensation technique. With reuse
of a Rel-17 enhanced TCI states activation/deactivation MAC CE
structure, as shown in FIG. 21, each codepoint of TCI field in DCI
for UE-specific PDSCH may be mapped to up to two TCI states. With
this structure, if Ci=0 (i.e., TCI codepoint in DCI indicates a TCI
state ID that only has one mapped TCI state), a PDSCH transmission
may be a single TRP and if Ci=1 (i.e., TCI codepoint in DCI
indicate a TCI state ID that has two mapped TCI states), a PDSCH
transmission may be a Rel-17 SFN scheme.
[0167] Both Rel-17 SFN schemes and Rel-16 non-SFN schemes (i.e.,
SDM, FDM and TDM schemes) may be beneficial for HST deployment
scenarios. The Rel-17 SFN schemes may provide high
reliability/coverage for a cell edge or high speed UEs while Rel-16
non-SFN schemes may provide high throughput for a cell center or
low speed UEs. Hence, the network should support dynamic
switching/indication of the scheduled PDSCH between Rel-16 non-SFN
and Rel-17 SFN schemes.
[0168] TRP-specific TRS transmission with precompensated frequency
offset may involve two separate QCL types, one for delay-related
large-scale profile (i.e., a new QCL type) and one for a
Doppler-shift related large-scale profile (i.e., QCL type B) in
addition to QCL type D. That means that up to three different QCL
types may be introduced in one TCI state to handle TRS transmission
with precompensated frequency offset. This enhanced TCI state may
be an indication of a Rel-17 SFN scheme. A UE may determine that
PDSCH is transmitted in a Rel-17 SFN scheme or in Rel-16 non-SFN
schemes based on a number of different QCL types defined inside the
indicated TCI state.
PTRS Enhancement and CPE Compensation
[0169] In Rel-17, PDCCH and PDSCH in HST-SFN scenarios may be
transmitted in SFN manner with two TCI-states. The PDSCH
transmission with two TCI states may involve two Phase Tracking
Reference Signal (PTRS) ports (each TCI state corresponding to one
TCI state), for accurate phase tracking at a UE particularly when
different panels are used to receive PDSCHs transmitted from
different TRPs simultaneously.
[0170] The current specification supports two PTRS ports for SDM
scheme in multi-TRP in which two TCI states may be indicated by one
TCI code point. The first PTRS port may be associated with the
lowest indexed DMRS port within the DMRS ports corresponding to the
first indicated TCI state and second PTRS port may be associated
with the lowest indexed DMRS port within the DMRS ports
corresponding to the second indicated TCI state. To expand the
current specification for multi-TRP situations in HST-SFN
scenarios, two port PTRS may be supported to provide accurate phase
tracking at a UE in which each PTRS port corresponds to one TCI
state.
[0171] Two scenarios may be considered for DMRS transmission in
HST-SFN scenarios, TRP-specific DMRS transmission (SFN
TRP-specific) and SFN manner DMRS transmission (SFN manner). For
both of these transmission types, support of two-port PTRS may
result in more accurate phase tracking at a UE.
[0172] In the current specification, the frequency density, time
density, resource-element offset and Energy Per Resource Element
(EPRE) ratio of PTRS are RRC configured through a higher layer
parameter PTRS-DownlinkConfig. With a two-port PTRS approach for
HST-SFN downlink transmission and following the current
specification, these parameters may be RRC configured for each of
PTRS ports. The number of PTRS ports may be RRC configured similar
to PTRS configuration for an uplink transmission in the current
specification. With dynamic switching between a Rel-17 SFN scheme
and a single TRP or Rel-15 SFN scheme, a maximum number of PTRS
ports may be semi-statically configured and a UE may ignore a
certain PTRS port when processing an unrelated PDSCH.
Alternatively, the number of PTRS ports may be dynamically
updated/activated. This may be done with an explicit RRC
configuration of two PTRS ports for Rel-17 SFN scheme that may be
activated through DCI. The number of PTRS ports may be implicitly
indicated by TCI codepoint in DCI. With enhanced TCI states
activation/deactivation MAC CE structure, each codepoint of a TCI
field in DCI for a UE-specific PDSCH may be mapped to up to two TCI
states. With this structure, if Ci=0 (i.e., a TCI codepoint in DCI
indicates a TCI state ID that only has one mapped TCI state), a
PDSCH transmission may be a single TRP with one port PTRS, and if
Ci=1 (i.e., a TCI codepoint in DCI indicates a TCI state ID that
has two mapped TCI states), a PDSCH transmission may be a Rel-17
SFN scheme with two PTRS ports. Alternatively, the signaling of two
PTRS ports may be done through a MAC CE activation.
Two Port PTRS in TRP-Specific DMRS Transmission
[0173] Channel estimation may be performed orthogonally for each
TRP based on the corresponding DMRS antenna port for a TRP-specific
DMRS transmission scheme so the phase noise may be estimated and
compensated for each TRP orthogonally with two PTRS ports
assumption in which each PTRS port corresponds to one TRP (i.e.,
TCI state). The association of two TCI states and DMRS may be
either through a comb-like allocation in which even-comb REs may be
assigned to the first TCI state (i.e., the first TRP) and odd-comb
REs may be assigned to the second TCI state (i.e., the second TRP).
Alternatively, a TD-OCC manner allocation may be used in which two
orthogonal DMRS ports in one CDM group may be assigned to two
different TCI states. In both these scenarios, the first PTRS port
may be associated with the lowest indexed DMRS port within the DMRS
ports corresponding to the first TRP (i.e., the first indicated TCI
state) and second PTRS port may be associated with the lowest
indexed DMRS port within the DMRS ports corresponding to the second
TRP (i.e., the second indicated TCI state).
Two Port PTRS in SFN-manner DMRS Transmission
[0174] For a SFN-manner DMRS transmission, the same REs may
correspond to two different TCI states. That is, the same DMRS
ports may be used by both TRPs simultaneously and DMRS experiences
a composite channel. In such a situation, consideration of two PTRS
ports transmitted in an SFN manner may not provide much benefit to
a UE because channel estimation may be based on composite channel
and the same REs may be associated to two PTRS ports with two
different indicated TCI state. To avoid two PTRS ports being
associated with the same REs having two different TCI states, a
PTRS may be transmitted in TRP-specific manner while DMRS and PDSCH
may be transmitted in a SFN manner. In this type of situation, the
first PTRS port may be associated with the lowest indexed DMRS port
within the DMRS ports corresponding to the first TRP (i.e., the
first indicated TCI state) and second PTRS port may be associated
with a predetermined/preconfigured indexed DMRS port within the
DMRS ports corresponding to the second TRP (i.e., the second
indicated TCI state). The RE association information for the second
PTRS port may be RRC configured or dynamically indicated to the UE,
or it may be the second lowest indexed DMRS port. The association
of two TCI states and PTRS transmitted from two TRPs may be either
comb-like or TD-OCC. This may allow a UE to estimate the
corresponding phase noise of each TRP independently. It is,
however, noted that because DMRS is transmitted in a SFN manner and
channel estimation may be based on the composite channel, separate
phase tracking for each TRP may involve a high complexity for a UE
implementation. One possible UE implementation may be a tap-based
phase-noise compensation in which the phase noise of each TRP may
be estimated and compensated for the corresponding channel tap.
That is, due to the fact that the channel modeling in HST-SFN
scenarios may be based on a line of sight (LOS) propagation path of
each TRP.
[0175] The transmitted signal from TRP.sub.i in HST-SFN scenarios
in the time domain may be written as:
x i .function. ( n ) = k = 0 N - 1 .times. S .function. ( k )
.times. e j .times. 2 .times. .pi. .times. n N .times. k .times. e
j .times. .times. .phi. i .function. ( n ) = k = 0 N - 1 .times. S
.function. ( k ) .times. ( 1 + j .times. .times. .phi. i .function.
( n ) ) .times. e j .times. 2 .times. .pi. .times. .times. n N
.times. k .times. .times. i = 1 , 2 ( 1 ) ##EQU00001##
[0176] The transmitted signal from TRP.sub.i may be written in the
frequency domain as:
X i .function. ( k ) = 1 N .times. n = 0 N - 1 .times. x .function.
( n ) .times. e j .times. - 2 .times. .pi. .times. .times. n N
.times. k = 1 N .times. n = 0 N - 1 .times. l = 0 N - 1 .times. S
.function. ( l ) .times. ( 1 + j .times. .times. .phi. i .function.
( n ) ) .times. e j .times. - 2 .times. .pi. .times. .times. n N
.times. ( l - k ) = S .function. ( k ) .times. ( 1 + j .times. 1 N
.times. n = 0 N - 1 .times. .phi. i .function. ( n ) ) + j N
.times. n = 0 N - 1 .times. l = 0 , .noteq. k N - 1 .times. S
.function. ( l ) .times. .phi. i .function. ( n ) .times. e j
.times. 2 .times. .pi. .times. n N .times. ( l - k ) .times.
.times. i = 1 , 2 ( 2 ) ##EQU00002##
[0177] in which .phi..sub.i(n) is the phase noise of TRP.sub.i and
S(k) is transmitted data on subcarrier k. Note that S(k) may be the
same for both TRPs in HST-SFN scenarios. Equation (2) may be
summarized as below:
X i .function. ( l ) = S .function. ( k ) .times. ( 1 + j .times.
.times. .phi. _ i .function. ( n ) ) + j N .times. n = 0 N - 1
.times. l = 0 , .noteq. k N - 1 .times. S .function. ( l ) .times.
.phi. i .function. ( n ) .times. e j .times. 2 .times. .pi. .times.
.times. n N .times. ( l - k ) .times. .times. i = 1 , 2 ( 3 )
##EQU00003##
in which .phi..sub.i(n) is the Common Phase noise Error (CPE) of
TRP.sub.i and may be derived as:
.phi. i .function. ( n ) = 1 N .times. n = 0 N - 1 .times. .phi. i
.function. ( n ) .times. .times. i = 1 , 2 ( 4 ) ##EQU00004##
[0178] The second sum component in Eqs. (2) and (3) is the ICI part
due to channel variation within an OFDM symbol, which may be caused
by the phase noise error. The received signal at a UE may be
derived as follow in frequency domain as:
Y .function. ( k ) = i = 1 2 .times. H i .function. ( k ) .times. X
i .function. ( k ) = S .function. ( k ) .times. i = 1 2 .times. H i
.function. ( k ) .times. ( 1 + j .times. .phi. i ) + j N .times. i
= 1 2 .times. H i .function. ( k ) .times. n = 0 N - 1 .times. l =
0 , .noteq. k N - 1 .times. S .function. ( l ) .times. .phi. i
.function. ( n ) .times. e j .times. 2 .times. .pi. .times. .times.
n N .times. ( l - k ) + W .function. ( k ) ( 5 ) ##EQU00005##
in which w(n) is the additive white Gaussian noise. If the ICI part
is treated as additive noise and is included in W(k), the received
signal may be simplified and rewritten as:
Y .function. ( k ) = i = 1 2 .times. H i .function. ( k ) .times. X
i .function. ( k ) = S .function. ( k ) .times. i = 1 2 .times. H i
.function. ( k ) .times. ( 1 + .phi. i ) + W .function. ( k ) ( 6 )
##EQU00006##
[0179] FIG. 22 shows a block diagram of an example embodiment of a
UE receiver 2200 for demodulating and decoding the received data.
The UE receiver 2200 may include a timing synchronization unit
2201, a CP-OFDM demodulation block 2202, a channel estimation block
2203, a phase noise estimation and compensation block 2204, a MIMO
detection block 2205 and a decoding block 2206 connected as shown.
The different functional blocks of the UE receiver 2200 may be
provided by modules and/or circuits. The channel estimation block
2203 may estimate the channel based on the received DMRS and
because DMRS may be transmitted in SFN manner, the channel
estimation may be based on a composite channel. That is, the
estimated channel in frequency domain is H.sub.est
(k)=H.sub.1(k)+H.sub.2 (k) with which a received signal is
equalized. However, as shown in Eqs. (5) and (6), the phase-noise
compensation involves a TRP-specific channel estimation. To address
this issue, an implementation of a UE receiver may include a
tap-based phase-noise compensation technique.
[0180] Modeling of the propagation channel in HST-SFN scenarios may
be based on LOS propagation path of TRPs. In HST-SFN scenarios
having two TRPs, a channel may be represented by a two-tap model in
the time domain in which each tap corresponds to the LOS path from
one TRP. That is, the time domain channel model is:
h .function. ( n ) = i = 1 2 .times. h i .times. .delta. .function.
( n - .tau. .about. i ) ( 7 ) ##EQU00007##
in which h.sub.i is the complex channel gain (i.e.,
h.sub.i=a.sub.ie.sup.j.theta.i) corresponding to the Line of Sight
(LOS) propagation path from TRP.sub.i,
.tau. .about. i = .tau. i T s .times. / .times. N ##EQU00008##
is tap delay quantized to the time-domain resolution and T.sub.s is
the symbol duration including CP. In other words, although the
channel estimation block in FIG. 22 estimates the composite channel
because the channel structure in the time domain may be tap-based
per TRP. The estimated channel for each TRP (i.e., H.sub.i(k)) may
possibly be derived from the estimated composite channel (i.e.,
H.sub.est(k)).
[0181] This may be provided by an extra functional block to perform
TRP-specific channel estimation by taking the estimated channel
H.sub.est (k) into the time domain and then separately taking each
tap of the time-domain channel (i.e., h.sub.i in Eq. (7)) back into
frequency domain. This enables TRP-specific equalization for PTRS
and TRP-specific CPE estimation at a UE. This more accurate phase
tracking may enable higher throughput at the expense of a higher
complexity.
[0182] FIG. 23 shows an example block diagram of a UE receiver 2300
according to the subject matter disclosed herein. The UE receiver
2300 may include a timing synchronization unit 2301, a CP-OFDM
demodulation block 2302, a channel estimation block 2303, a
TRP-specific channel estimation block 2304, a phase noise
estimation and compensation block 2305, a MIMO detection block 2306
and a decoding block 2307 connected as shown. The different
functional blocks of the UE receiver 2300 may be provided by
modules and/or circuits.
[0183] For FR2 applications (i.e., frequency bands from 24.25 GHz
to 52.6 GHz), an example UE implementation may be that a UE would
use two different panels to control the corresponding beam of each
TRP independently. That is, separate transmitter/receiver chains
may be implemented for multi-TRP transmission in a HST-SFN
scenario.
[0184] FIG. 24 shows a block diagram of an example embodiment of a
UE receiver 2400 having separate receiver chains according to the
subject matter disclosed herein. The UE receiver 2400 may include a
first receiver chain that may include a timing synchronization unit
2401, a CP-OFDM demodulation block 2402, a channel estimation block
2403, and a phase noise estimation and compensation block 2404
connected as shown, and a second receiver chain that may include a
timing synchronization unit 2411, a CP-OFDM demodulation block
2212, a channel estimation block 2213, and a phase noise estimation
and compensation block 2214 connected as shown. The outputs of the
blocks 2404 and 2414 are coupled into a MIMO detection block 2405
and a decoding block 2406, which are connected as shown.
[0185] With the UE receiver 2400, although the DMRS may be
transmitted in a SFN manner, the received signal from each TRP may
be processed independently, which allows channel estimation and
phase-noise compensation to be performed separately for each TRP
communication. The demodulated data corresponding to each TRP may
then be combined, equalized and decoded.
Default Beam Determination in Multi-TRP Transmission
[0186] FIGS. 25 and 26 respectively depict a single-DCI and
Multi-DCI M-TRP transmission schemes according to the subject
matter disclosed herein. Multiple Transmit and Receive Points
(M-TRP) were originally introduced in Rel-15 as a solution to
improve cell-edge performance. In a M-TRP transmission scheme,
different antenna ports of one or different channels may be within
multiple TRPs that are typically non-co-located. M-TRP
transmissions may be categorized into a single-DCI category and a
multi-DCI M-TRP category. With a single-DCI M-TRP, a single PDCCH
is transmitted to schedule one or multiple PDSCHs. The PDSCH may be
transmitted from different TRPs so that different layers may be
transmitted from different TRPs. Alternatively, all the layers of a
PDSCH may be transmitted from one TRP while multiple of PDSCHs may
be multiplexed in time or frequency domain within the same
transport block (TB). In multi-DCI M-TRP transmission, each TRP
transmits their own PDCCH and DCIs. Each DCI schedules one PDSCH
with two-layer transmission. All of the layers of a given PDSCH may
be transmitted from the antenna ports within the same TRP.
[0187] Different multiplexing schemes may be applied to PDCCH
transmission. With TDM multiplexing, two sets of symbols of the
transmitted PDCCH/two non-overlapping (in time) transmitted PDCCH
repetitions/non-overlapping (in time) multi-chance transmitted
PDCCH may be associated with different TCI states. With FDM
multiplexing, two sets of resource element group (REG)
bundles/control channel elements (CCEs) of the transmitted
PDCCH/two non-overlapping (in frequency) transmitted PDCCH
repetitions/non-overlapping (in frequency) multi-chance transmitted
PDCCH may be associated with different TCI states. With SDM
(non-transparent SFN), two different DMRS ports are each associated
with one different TCI state. Rel-17 does not support SDM PDCCH
schemes. With SFN, PDCCH DMRS may be associated with two TCI states
in all REGs/CCEs of the PDCCH.
[0188] For a non SFN M-TRP PDCCH transmission the following
possibilities of no-repetition, repetition and multi-chance may be
considered. For no repetition, one encoding/rate matching may be
used for a PDCCH with two TCI states. With this scheme, a single
PDCCH candidate may be with two different TCI states. That is, some
specific CCE/REGs of the candidate may be associated with the first
TCI state and the rest of the CCE/REGs are associated with the
second TCI state. For repetition, encoding/rate matching may be
based on one repetition, and the same coded bits may be repeated
for the other repetition. Each repetition has the same number of
CCEs and coded bits, and corresponds to the same DCI payload. For
multi-chance, separate DCIs may schedule the same
PDSCH/PUSCH/RS/TB/etc. or result in the same outcome.
[0189] With any of the aforementioned transmission schemes, to
enable a PDCCH transmission with two different TCI states one
approach may be to associate one control resource set (CORESET)
with two different TCI states. Following different multiplexing
schemes for PDCCH transmission, the Schemes A-C below may be used
with one CORESET with two active TCI states:
[0190] FIG. 27A depicts a Scheme A in which one PDCCH candidate (in
a given SS set) may be associated with both TCI states of the
CORESET according to the subject matter disclosed herein.
[0191] FIG. 27B depicts a Scheme B in which two sets of PDCCH
candidates (in a given SS set) may be respectively associated with
the two TCI states of the CORESET according to the subject matter
disclosed herein.
[0192] FIG. 27C depicts a Scheme C in which two sets of PDCCH
candidates may be associated with two corresponding SS sets in
which both SS sets may be associated with the CORESET and each SS
set may be associated with only one TCI state of the CORESET
according to the subject matter disclosed herein.
[0193] For Schemes B and C, the following two cases may be
considered for mapping between different PDCCH candidates with
different TCI states.
[0194] Case 1: Two (or more) PDCCH candidates may be explicitly
linked together (UE knows the linking before decoding).
[0195] Case 2: Two (or more) PDCCH candidates may not be explicitly
linked together (UE does not know the linking before decoding).
[0196] As a different alternative to associate PDCCH candidates to
two different TCI states, one SS set may be associated with two
different CORESETs in which each CORESET is associated with a TCI
state. A different SS and CORESET multiplexing scheme may also be
possible to allow multiple TCI state for PDCCH candidates. With
this scheme, two SS sets are associated with two CORESETs in which
each CORESET may be configured with a different TCI state.
Default Beam and RS Specification
[0197] For a single DCI-based NCJT in Rel-16, a UE may be
configured with up to three CORESETs and ten search space sets on
each of up to four Bandwidth Parts (BWP) on a serving cell. A
search space set may be associated with only one CORESET and one
TCI state. Having a PDCCH with two TCI states in multi-TRP scenario
affects the default beam and RS specification because in the
current specification they are specified with consideration of one
TCI state for the CORESET. To illustrate, a default beam for PDSCH
is derived based on TCI state of the CORESET with lowest ID. Also,
a default spatial relation and a pathloss RS if not configured may
be derived based on a TCI state of the CORESET having lowest ID or
the TCI state having the lowest ID for PDSCH. In a beam-failure
recovery, beam-failure detection RS, if not explicitly configured,
is derived based on a TCI state for a responsive CORESET used for
monitoring PDCCH.
[0198] The default TCI state of the PDSCH may be determined to be
as a single TCI state or a pair of TCI states. While the single TCI
state may be applicable to PDSCH transmission schemes with single
or multiple TCI states, the pair of TCI states may only be
applicable to the PDSCH transmission schemes having two different
TCI states.
Single TCI State Default Beam
[0199] To determine the default beams for PDSCH receptions, the
following three methods may be possible.
[0200] Method 1 (Ignore CORESETs with two TCI states): In general,
for a multi-TRP scenario, one solution to prevent any ambiguity on
the default beam and RS determination at a UE may be that the
default beam and RS specification may be determined only based on
CORESETs with a single TCI states. That is, a default beam for
PDSCH, a default spatial relation and a pathloss RS may be derived
based on TCI state of the CORESET having a lowest ID among the
CORESETs with a single TCI states. With Method 1, Rel-15 behavior
may be reused with an exception that this method may only consider
CORESETs that are associated with one TCI state.
[0201] Method 2 (CORESET having the lowest ID with two TCI states
is an error case): An alternative solution may be that the
specification does not allow the lowest CORESET index to be
configured with two TCI states. With this solution, a UE may not be
expected to be configured with CORESETs and the associated one or
two TCI states so that the CORESET having the lowest ID in the
latest slot that UE monitors PDCCHs may be associated with two
different TCI states. This may be a reuse of Rel-15 behavior.
[0202] Method 3 (reference TCI-state/TRP): Still another approach
may be that one of the TRPs and/or its corresponding TCI state may
be configured as the reference TRP and/or reference TCI state in
which a default beam and RS specification may be derived based on
that specific TCI state. Method 3 may be described as follows.
[0203] Each TCI state may additionally be associated with a TRP
through a TRP index 1 or 2. Each CORESET may be associated with one
or two TCI states. In particular, a MAC-CE activates either a
single TCI state or a pair of TCI states (TCI state #1, TCI state
#2). A gNB may configure a UE via a RRC with a reference TRP index
t.sub.ref.di-elect cons.{1,2} for default beam determination. A UE
determines the default TCI state from CORESETs having a TCI state
associated to the reference TRP index t.sub.ref. Among the CORESETs
that include a TCI states associated with the reference TRP index,
a CORSET having the lowest ID is selected. An example is shown
below in the Table 2 in which the UE may be assumed to be
configured with a reference TRP index t.sub.ref=2. The default TCI
state may be TCI-State 3 in CORSET ID #2.
TABLE-US-00006 TABLE 2 Example default TCI state determination for
Method 3 CORSET ID Activated TCI states #0 TCI-State 1 with
t.sub.ref = 1 #1 TCI-State 2 with t.sub.ref = 1 #2 (TCI-State 1
with t.sub.ref =1, TCI-State 3 with t.sub.ref = 2) #3 (TCI-State 2
with t.sub.ref =1, TCI-State 5 with t.sub.ref = 2) #4 TCI-State 5
with t.sub.ref = 2 #5 TCI-State 4 with t.sub.ref = 2
[0204] Method 4 (A CORESET-independent reference TCI state entry
index): Method 4 may include the concept of a reference TRP that is
not defined. With this method, a UE may be configured with TCI
states in which there is no explicit association between the TCI
states and the TRPs. A MAC-CE may activate a one or more TCI states
for each CORESET. The activated TCI states may be in the form of a
P-tuple having P entries (TCI-State #i.sub.1, TCI-State #i.sub.2 .
. . , TCI-State #i.sub.P). P can be the same or different for
different CORESETs, P=1, 2, 3 . . . . A gNB may configure a UE with
a reference TCI state index i.sub.ref. Among CORESETs having a TCI
state tuple that includes an index i.sub.ref, a CORSET having the
lowest ID is selected. The default TCI state may then be
i.sub.ref-entry of the tuple associated with the selected
CORSET.
[0205] As an alternative, the reference TCI state entry index
i.sub.ref may be predetermined by being specified to always
consider a predetermined TCI state (e.g., the first or the second)
in each CORSET as the reference TCI state.
[0206] As an example, a gNB may configure UE with i.sub.ref=2. The
UE may determine the default TCI state from the CORESET that has at
least two TCI states, i.e., the activated tuple may be of length 2
or more. The second entry may be selected as the default TCI states
among those CORESETs.
[0207] The default beam may also always be determined from the
CORESET having the lowest CORESET ID regardless of the number of
active TCI states of a CORESET, configuration of reference TRP, or
reference TCI-state index. etc. This may be realized by Method 4
when a gNB configures the reference TCI state index as i.sub.ref=1.
Method 4 may alternatively described as below.
[0208] Method 4-0 (a special case of Method 4): The default TCI
state may always be determined from the CORESET having the lowest
CORESET ID. If the CORESET has a single TCI state, the TCI state
may be determined as the default TCI state. If the CORESET has
multiple TCI states, the default TCI state may be determined to be
the i.sub.ref-th TCI state. The i.sub.ref may be configured to the
UE via RRC as the reference TCI state index or may be
pre-determined. It may be specified to always consider a
predetermined TCI state (e.g., the first or the second state) in
each CORSET as the reference TCI state. Alternatively, the
reference index may be configured for each CORSET separately.
[0209] Method 5 (a CORESET-dependent reference TCI state entry
index): With this method, a UE may be configured with TCI states in
which there may be no explicit association between the TCI states
and the TRPs. A MAC-CE may activate one or more TCI states for each
CORESET. The activated TCI states may be in a form of a P-tuple
with P entries (TCI-State #i.sub.1, TCI-State #i.sub.2 . . . ,
TCI-State #i.sub.P). P may be the same or may be different for
different CORESETs, P=1, 2, 3 . . . . A gNB may configure a UE with
a reference TCI state index i.sub.ref for each CORSET. The default
TCI state may then be selected from the TCI states of the CORESET
having lowest CORESET ID. The default TCI state may be the
i.sub.ref-entry of the tuple associated with the selected CORESET
in which i.sub.ref may be the reference TCI state index of the
selected CORSET.
[0210] An HST-SFN transmission may be a coherent joint transmission
that employs only one PDCCH to allocate one set of PDSCH resources.
That is, the same PDCCH may be transmitted from multiple TRPs
simultaneously. From a UE perspective, an extra downlink
transmission may be interpreted as an additional downlink
delay-spread component originated from a single TRP. Having PDCCH
with two TCI states in an HST scenario may mean that a CORESET in
Rel-17 may be configured with two TCI states. The default beam and
RS specification in HST scenario may follow Rel-16 behavior using
the TCI state of PDCCH transmitted from the reference TRP. The
reference TRP may be the TRP that is being used by a gNB as the
reference for frequency offset compensation in TRP-based frequency
offset precompensation scheme. This may make the reference TRP as
the primary TRP especially in the case of beam-failure events. The
reference TRP may be semi-statically indicated with a certain TCI
state to UE and the default TCI state may be selected from the
CORESET having the lowest ID that has a TCI state associated to the
reference TRP. Another approach may be that one of the TCI states
in the CORESET may be semi-statically indicated to the UE as a
reference TCI state or it may be specified to always consider a
predetermined TCI state (i.e., the first or the second) in each
CORSET as the reference TCI state. That reference TCI state may
then be used as the default TCI state to determine default beam and
RS. Another solution is that the default beam and RS specification
may be determined only based on CORES ETs having a single TCI
states or the specification may make the lowest CORESET index in
HST scenario always have a single TCI state.
[0211] A TCI state format may include two different pairs of QCL
info and reference signals as shown below in bold:
TABLE-US-00007 TCI-State-r17 ::= SEQUENCE { tci-StateId
TCI-StateId, qcl-Type1 QCL-Info, qcl-Type2 QCL-Info OPTIONAL, --
Need R qcl-Type1-r17 QCL-Info, qcl-Type2-r17 QCL-Info OPTIONAL, --
Need R ...
[0212] With this new enhanced Rel-17 TCI format, a PDCCH having two
TCI states in a HST scenario may be associated with a CORESET
having one TCI state. The default beam and RS specification may
thus follow Rel-16 behavior and may be derived based on the TCI
state of the CORESET having the lowest ID. The TCI state of the
CORESET having the lowest ID, however, may contain two pairs of QCL
RS and may cause ambiguity for the default beam and RS
determination at a UE. To address this issue, one solution may be
that the default beam and RS specification may only be determined
based on CORESETs having TCI states that only contain one pair of
QCL information (i.e., a legacy TCI). Alternatively, the
specification may restrict the lowest CORESET index in an HST
scenario to always have a legacy TCI state and not the enhanced
Rel-17 format. Another approach may be that one of the QCL
information pairs or one of the QCL RS in the TCI state of the
CORESET having lowest ID may be semi-statically indicated to the UE
as a reference QCL info pair or the reference QCL RS. It may also
be specified to always consider a predetermined (i.e., the first or
the second) QCL info pair/QCL RS in each TCI state as the reference
to be used as the default beam and RS. Another approach may be that
a reference TRP may be semi-statically indicated with a QCL
information pair to a UE, and a default beam and RS may be selected
from the CORESET having the lowest ID that has a TCI state
associated to the reference TRP.
[0213] To provide increased reliability of PDCCH transmission in
multi-TRP cells, especially in a scenario in which a TRP is likely
to be blocked, different PDCCH schemes may be considered. Different
PDCCH schemes have been presented and with these schemes, a PDCCH
may be repeated within or across different SS sets. It may also be
transmitted with a scheme referred to as multi-chance in which the
multiple PDCCHs schedule the same PDSCH/PUSCH or uplink/downlink
channel/signal. From a different point of view, a repeated PDCCH
may be associated with one or two CORESETs. As an example, a PDCCH
may be repeated across or within a Synchronization Signal (SS) set.
As a different example, a PDCCH may be transmitted so that its
first repetition is transmitted in a first SS associated with
CORESET #1 and the second repetition may be transmitted in a second
SS set associated with CORESET #2. FIGS. 28A-28D depict examples of
repetition schemes disclosed herein.
[0214] With one CORESET and two TCI states, the default PDCSH beam
may be determined based on the TCI state of the CORESET that is
associated with the latest repetition of the PDCCH in the slot.
[0215] Method 6 (Latest TCI state associated with the repeated
PDCCHs within the same CORESET): With this method, each CORESET may
be associated with one or two TCI states. In particular, a MAC-CE
either actives a single TCI state for a CORESET, in which case it
also indicates which TRP number the activated TCI state may be
associated with, or the MAC-CE activates a pair of TCI states (TCI
state #1, TCI state #2) in which the TCI states #1 and #2
correspond to the first and second TRPs, respectively. The default
TCI state is selected from the CORESET having the lowest ID that
are associated with two different TCI states. Among the two TCI
states of the CORESET having the lowest ID, the TCI state
associated with the latest SS set is selected as the default TCI
state.
[0216] Method 7 (Latest TCI state associated with the repeated
PDCCHs with different CORESETs): With this method, each CORESET may
be associated with one or two TCI states. In particular, a MAC-CE
either actives a single TCI state for a CORESET, in which case the
MAC-CE also activates the TRP number that this TCI state may be
associated with, or the MAC-CE activates a pair of TCI states (TCI
state #1, TCI state #2) in which the TCI states #1 and #2
correspond to the first and second TRPs, respectively. The default
TCI state may be selected from the CORESET with the lowest ID.
[0217] If the CORSET is associated with two different TCI states.
The TCI state associated with the latest SS set is selected as the
default TCI state from among the two TCI states of the CORESET
having with lowest ID.
[0218] If the CORSET is associated with single TCI state and it is
linked to a linked CORESET, the default TCI state may be selected
to be that of the CORESET or the linked CORSET, whichever ends
later in the slot.
[0219] Alternatively, either of the Methods 6 and 7 may be used
with the modification that the earliest SS set is selected among
the linked sets.
Two TCI State Default Beam
[0220] As previously mentioned, the default beam may also be
determined as a pair of TCI states.
[0221] The default pair of TCI state may be determined from the
configured CORESETs having two different TCI states.
[0222] Method 8 (Default TCI states as a pair and
CORESET-dependent): If a UE is configured with one or more CORESETs
in which at least one CORESET may be associated with two TCI
states, the default TCI state of the PDSCH may be determined as
follows. The UE determines the CORESET having the lowest ID among
the CORESETs that are associated with two TCI states. The default
TCI states may then be determined as the pair of TCI states
associated with the CORESET having lowest CORESET ID.
[0223] Method 8 may be applicable when there is at least one
CORESET having two different TCI states. If there is no CORESET
with two TCI states, the default beam may be determined as the TCI
state of the CORESET with lowest CORESET ID.
[0224] Alternatively, the default TCI state may be determined to be
selected from the set single or pair of TCI states activated by
MAC-CE for PDSCH reception.
[0225] Method 9 (Default TCI states as a pair and lowest PDSCH
codepoint): When a MAC CE activates the set of TCI states for the
PDSCH reception so that there may be at least one TCI codepoint
with two different TCI states, the default TCI states of the PDSCH
may be determined as the TCI states corresponding to the lowest TCI
codepoint among the TCI codepoints containing two different TCI
states.
TCI State Application to PDSCH
[0226] Once a UE has determined the default TCI state pair as (A,
B), if the PDSCH follows the default TCI state, the UE should apply
the TCI states (A, B) according to the mapping. Prior to DCI
decoding, however, the UE may not know which resources have been
used for each TCI states in the PDSCH transmission. In the
following, a solution is provided that addresses this issue.
SDM, SFN and HST PDSCH
[0227] With SDM PDSCH schemes, a certain number of ports of PDSCH
may be associated with the first TCI state and certain others may
be associated with the second TCI states. Therefore, regardless of
the time/frequency domain resource allocation, a UE may be expected
to receive the OFDM symbols with both TCI states without requiring
the DCI decoding. Similarly with SFN and HST PDSCHs, a DMRS port
may be associated with two TCI states and a UE does not need the
resource allocation to apply the TCI states.
TDM PDSCH
[0228] With TDM PDSCH, a UE may need to know the resource
allocation to apply the default TCI states. With one solution, a
DCI decoding delay time may be defined to acknowledge the DCI
decoding delay. The UE receives the symbols before the DCI decoding
delay with the first TCI state and receives the next symbols
according to the indicated resource allocation in the DCI. The
following methods may define the UE behavior. In the following
methods, "default TCI state threshold time" may be defined
according to the UE capability and may be measured from the end of
the PDCCH scheduling the PDSCH.
[0229] Method 10 (One state until DCI decoding delay and two states
until threshold): If a UE is configured with an RRC parameter
indicating the reception of PDSCH with two default TCI states, and
at least one TCI codepoint indicates two TCI states, and UE is
configured to receive a single-DCI M-TRP TDM PDSCH, UE may be
configured via RRC or may be given a predefined DCI decoding delay
T.sub.DCI decoding. The UE may determine the default TCI states as
(A, B) and receives the symbols as follows.
[0230] From the first symbol of the CORESET in which a UE monitors
the PDCCH until T.sub.DCI,decoding after the end of the CORSET, the
UE receives the symbols assuming the first TCI state A. From
T.sub.DCI,decoding after the end of the CORSET until the default
TCI state threshold time, the UE receives the symbols according to
the time domain resource allocation indicated by the DCI with both
TCI states A and B.
[0231] FIG. 29 depicts an example of PDSCH scheduling and UE
behavior according to Method 10. From the start of the PDCCH to the
second vertical dashed line 2901, the UE receives symbols with the
first TCI state 2902 from the second vertical dashed line 2901, the
UE receives the symbols according to the indicated time-domain
resource in the DCI. The time domain resource may indicate for the
UE to receive the PDSCH occasions as shown in FIG. 29, so the UE
will know to receive the second PDSCH occasion with the second TCI
state 2903.
[0232] In Method 10, a UE receives the symbols before the DCI
decoding delay with a single TCI state. This may prevent a gNB from
scheduling two TCI states before the DCI decoding delay. This issue
is address in Method 11.
[0233] Method 11 (Two states until DCI decoding delay and two
states until threshold): FIG. 30 depicts an example of method 11
according to the subject matter disclosed herein. If a UE is
configured with an RRC parameter indicating the reception of PDSCH
with two default TCI states, and at least one TCI codepoint
indicates two TCI states, and the UE is configured to receive a
single-DCI M-TRP TDM PDSCH, the UE may be configured via RRC or may
be given a predefined DCI decoding delay T.sub.DCI decoding. The UE
may determine the default TCI states as (A, B) and receives the
symbols as follows.
[0234] From the first symbol of the CORESET in which the UE
monitors the PDCCH until T.sub.DCI,decoding after the end of the
CORSET, the UE may receive the symbols assuming the first TCI state
A and second TCI state B according to a fixed time locations in
which the symbols are mapped to the first and second TCI states.
From T.sub.DCI,decoding after the end of the CORSET until the
default TCI state threshold time, the UE receives the symbols
according to the time domain resource allocation indicated by the
DCI with both TCI states A and B.
[0235] Alternatively. a UE may only receive one TCI state before
the threshold or two TCI states on fixed time locations.
[0236] Method 12 (One state until threshold): If a UE is configured
with an RRC parameter indicating the reception of PDSCH with two
default TCI states, and at least one TCI codepoint indicates two
TCI states, and UE is configured to receive single-DCI M-TRP TDM
PDSCH, the UE may determine the default TCI states as (A, B) and
receive the symbols with TCI states as follows.
[0237] FIG. 31 depicts an example of method 12 according to the
subject matter disclosed herein. From the first symbol of the
CORESET until the default TCI state threshold time, the UE receives
the symbols with TCI state A.
[0238] Method 13 (two states until threshold): FIG. 32 depicts an
example of method 13 according to the subject matter disclosed
herein. If a UE is configured with an RRC parameter indicating the
reception of PDSCH with two default TCI states, and at least one
TCI codepoint indicates two TCI states, and UE is configured to
receive single-DCI M-TRP TDM PDSCH, the UE may determine the
default TCI states as (A, B) and receive the symbols with TCI
states as follows.
[0239] From the first symbol of the CORESET until the default TCI
state threshold time, the UE receives the symbols with both TCI
state A and B according to fixed time locations in which the
symbols are mapped to the first and second TCI states.
How to Determine the Fixed Time Locations
[0240] The fixed time locations in Methods 11 and 13 are symbols
that a UE receives using a specific TCI states among the two
default states. To determine the time locations for each TCI state,
"fixed window" is first determined. The symbols inside the "fixed
window" may be assigned to one of the two TCI states. The window
starts at the first symbol of the CORESET and may end at the
threshold time or the time indicated by the DCI decoding delay or
the time indicated by the default TCI state threshold, the start of
the next earliest CORESET in which the UE monitors PDCCH.
Case 1: Intra-Slot TDM
[0241] In the case of an intra-slot TDM, the "fixed window" starts
at the starting symbol of the CORESET and ends either at the start
of the earliest next CORESET or the time indicated by DCI decoding
delay, whichever is earlier. Once the fixed window has been
determined, the set symbols in the window are mapped to the first
and second TCI states as follows.
[0242] Two chunk in each slot: If a slot has N symbols in the fixed
window, the first N.sub.1 symbols are mapped to the first TCI
states and the second N-N.sub.1 symbols are mapped to the second
TCI states in which N.sub.1 may be RRC configured, or fixed
predetermined, or N.sub.1=.left brkt-bot.N/2.right brkt-bot.. A
typical choice for a slot with N symbols in the window is
N.sub.1=.left brkt-bot.N/2.right brkt-bot..
[0243] FIG. 33 depicts an example of an intra-slot TDM according to
the subject matter disclosed herein.
[0244] Multiple consecutive chunks with alternating TCI states: As
a different approach, if a slot has N symbols in the fixed window,
the N symbols are grouped in L groups in which group 1 includes the
first N.sub.1 symbols, group 2 includes the next N.sub.2 symbols,
group 3 includes the next N.sub.3 symbols, and so on, in which each
group includes an even number of symbols except possibly the first
group or the last group. For group with an even number of symbols,
the first half of symbols may be mapped to the first TCI state and
the second half may be mapped to the second TCI state. For a group
with odd number 2K+1 symbols, the first K symbols may be mapped to
the first TCI state and the next K+1 may be mapped to the second
TCI state. FIG. 34 depict an example of multiple consecutive chunks
with alternating TCI states with L=2 according to the subject
matter disclosed herein.
Case 2: Inter-Slot TDM
[0245] Schemes similar to an intra-slot may be considered for
inter-slot TDM with the modification that the TCI state alternates
in two consecutive slots. In case of inter-slot TDM, the "fixed
window" starts at the starting symbol of the CORESET and ends
either at the start of the earliest next CORESET or the time
indicated by DCI decoding delay, whichever is earlier. Once the
fixed window has been determined, the set of symbols in the window
may be mapped to the first and second TCI states as follows.
[0246] Multiple consecutive slots with alternating TCI states: If N
consecutive slots overlap with the fixed window, the symbols of the
first, third, fifth and . . . slots may be mapped to the first TCI
states, and the symbols of the second, fourth, sixth and . . .
slots may be mapped to the second TCI state. FIG. 35 depicts an
example of multiple consecutive slots with alternating TCI states
based on an Inter-slot TDM case 2 according to the subject matter
disclosed herein.
FDM PDSCH
[0247] With a FDM PDSCH scheme, a first half of resource blocks may
be associated with the first TCI state and a second half may be
associated with the second TCI state. In principle, the default TCI
state and UE behavior for FDM PDSCH scheme may also be determined
with any of the methods 10 to 11 in which the fixed time locations
may be replaced by fixed frequency locations and the frequency
locations (RBs) may be mapped to the first and second TCI states. A
fixed window may be determined that includes a starting RB and a
length in terms of number of RB. A fixed window may alternatively
be defined by a set of bitmap that indicates which RB s are
included in the window. Once the window has been determined to
include N RBs, the first N.sub.1 RB s may be mapped to the first
TCI state and the second N-N.sub.1 RB s may be mapped to the second
TCI state.
[0248] An example of such schemes is as follows. The fixed window
may be chosen to be the entire active BWP. The active BWP may be
divided in half into two sets of equal number of RBs. A UE receives
the first sets of RBs with the first TCI state and the second set
with the second TCI state until the UE has decoded the DCI. After
the UE decodes the DCI, the UE receives the set of allocated PDSCH
RBs according to the frequency-domain allocation. To accommodate
with this behavior, a gNB may be expected to transmit the FDM PDCSH
so that a first half of scheduled RBs are in the first half of BWP
and the second half of scheduled RBs are in the second half of BWP.
FIG. 36 depicts an example of an FDM PDSCH scheme according to the
subject matter disclosed herein.
A Sample TP for TS 38.214
Antenna Ports Quasi Co-Location
[0249] <Unchanged Parts have been Omitted>
[0250] Independent of the configuration of tci-PresentInDCI and
tci-PresentDCI-1-2 in RRC connected mode, if the offset between the
reception of the DL DCI and the corresponding PDSCH is less than
the threshold timeDurationForQCL and at least one configured TCI
state for the serving cell of scheduled PDSCH contains qcl-Type set
to `typeD`, [0251] the UE may assume that the DM-RS ports of PDSCH
of a serving cell are quasi co-located with the RS(s) with respect
to the QCL parameter(s) used for PDCCH quasi co-location indication
of the CORESET associated with a monitored search space with the
lowest controlResourceSetId in the latest slot in which one or more
CORESETs within the active BWP of the serving cell are monitored by
the UE. In this case, if the qcl-Type is set to `typeD` of the
PDSCH DM-RS is different from that of the PDCCH DM-RS with which
they overlap in at least one symbol, the UE is expected to
prioritize the reception of PDCCH associated with that CORESET.
This also applies to the intra-band CA case (when PDSCH and the
CORESET are in different component carriers). [0252] If a UE is
configured with enableDefaultTCIStatePerCoresetPoolIndex and the UE
is configured by higher layer parameter PDCCH-Config that contains
two different values of coresetPoolIndex in different
ControlResourceSets, [0253] the UE may assume that the DM-RS ports
of PDSCH associated with a value of coresetPoolIndex of a serving
cell are quasi co-located with the RS(s) with respect to the QCL
parameter(s) used for PDCCH quasi co-location indication of the
CORESET associated with a monitored search space with the lowest
controlResourceSetId among CORESETs, which are configured with the
same value of coresetPoolIndex as the PDCCH scheduling that PDSCH,
in the latest slot in which one or more CORESETs associated with
the same value of coresetPoolIndex as the PDCCH scheduling that
PDSCH within the active BWP of the serving cell are monitored by
the UE. In this case, if the `QCL-TypeD` of the PDSCH DM-RS is
different from that of the PDCCH DM-RS with which they overlap in
at least one symbol and they are associated with same
coresetPoolIndex, the UE is expected to prioritize the reception of
PDCCH associated with that CORESET. This also applies to the
intra-band CA case (when PDSCH and the CORESET are in different
component carriers). [0254] If a UE is configured with
enableTwoDefaultTCI-States, and at least one TCI codepoint
indicates two TCI states, the UE may assume that the DM-RS ports of
PDSCH or PDSCH transmission occasions of a serving cell are quasi
co-located with the RS(s) with respect to the QCL parameter(s)
associated with the TCI states corresponding to the lowest
codepoint among the TCI codepoints containing two different TCI
states. When the UE is configured by higher layer parameter
repetitionScheme set to `tdmSchemeA` or is configured with higher
layer parameter repetitionNumber, the mapping of the TCI states to
PDSCH transmission occasions is determined according to clause
5.1.2.1 by replacing the indicated TCI states with the TCI states
corresponding to the lowest codepoint among the TCI codepoints
containing two different TCI states based on the activated TCI
states in the slot with the first PDSCH transmission occasion. The
UE may further assume that the DM-RS ports of PDSCH or PDSCH
transmission occasions on the set of symbols starting from the
first symbol of a CORESET in which the scheduling PDCCH is
transmitted to N.sub.3 symbols after the end of the CORESET are
quasi co-located with the RS with respect to the QCL parameter
associated with the first TCI state corresponding to the lowest
codepoint among the TCI codepoints containing two different TCI
states, where N.sub.3 is determined according to clause 9.2.3 of TS
38.213. In this case, if the `QCL-TypeD` in both of the TCI states
corresponding to the lowest codepoint among the TCI codepoints
containing two different TCI states is different from that of the
PDCCH DM-RS with which they overlap in at least one symbol, the UE
is expected to prioritize the reception of PDCCH associated with
that CORESET. This also applies to the intra-band CA case (when
PDSCH and the CORESET are in different component carriers). [0255]
In all cases above, if none of configured TCI states for the
serving cell of scheduled PDSCH is configured with qcl-Type set to
`typeD`, the UE shall obtain the other QCL assumptions from the
indicated TCI states for its scheduled PDSCH irrespective of the
time offset between the reception of the DL DCI and the
corresponding PDSCH.
[0256] <Unchanged Parts are Omitted>
Beam Failure
[0257] To address beam-failure recovery in HST scenario with
TRP-based frequency offset precompensation, two different scenarios
may be considered. First, beam failure happens for a reference TRP,
and second, beam failure happens for a non-reference TRP. For both
these scenarios, each TRP may be configured with up to two periodic
1-port CSI-RS for per BWP explicitly by RRC or implicitly by TCI
state for beam failure detection. Downlink RS for new beam
identification set may be based on SSB and CSI-RS and may be
configured explicitly and separately for each TRP. Besides, since
two TCIs are activated for PDCCH, each TCI state may implicitly
correspond to a beam failure detection RS for the corresponding
TRP, if not configured. When a beam failure happens for one of the
TRPs, the reception at UE may fall back to single TRP scenario.
That is, a UE should switch channel estimation and other signal
processing algorithm to a channel estimation and signal processing
algorithm that are used for single TRP transmission when the UE
detects a beam failure.
[0258] In HST-SFN scenarios with TRP-based frequency offset
precompensation, if a beam failure occurs for the reference TRP,
there would be some QCL information relation (i.e., Doppler-shift
related properties) breakage on non-reference TRP transmissions due
to beam failure of the reference TRP. To illustrate, when network
precompensates frequency offset for TRS and all other downlink
transmissions (including PDCCH, DMRS and PDSCH), the QCL RS of the
TRS transmitted from non-reference TRP may be the TRS transmitted
from the reference TRP or the QCL RS of the TRS transmitted from
the reference TRP with QCL type B. Similarly, when network
precompensates frequency offset for all downlink transmissions, but
not TRS, QCL RS for the PDCCH, PDSCH DMRS of non-reference TRP may
be the TRS transmitted from the reference TRP with QCL type B. That
means beam failure on a reference TRP transmission may also disrupt
the PDCCH and PDSCH reception at non-reference TRP. In this case,
one solution may be for the QCL information of the latest TRS
received from the reference TRP before beam failure has been
identified may be used for continuation of DL transmission from
non-reference TRP. That is, a UE only monitors the PDCCH using the
TCI state associated with the non-reference TRP and reuses the
associated TCI states of the reference TRP in the last received
CORESET for the latest slot before beam failure was identified by
the UE. The PDSCH reception may also be accordingly with reuse of
the associated TCI states of the reference TRP in the latest slot
before beam failure was identified by the UE.
[0259] Embodiments of the subject matter and the operations
described in this specification may be implemented in digital
electronic circuitry, or in computer software, firmware, or
hardware, including the structures disclosed in this specification
and their structural equivalents, or in combinations of one or more
of them. Embodiments of the subject matter described in this
specification may be implemented as one or more computer programs,
i.e., one or more modules of computer-program instructions, encoded
on computer-storage medium for execution by, or to control the
operation of data-processing apparatus. Alternatively or
additionally, the program instructions can be encoded on an
artificially-generated propagated signal, e.g., a machine-generated
electrical, optical, or electromagnetic signal, which is generated
to encode information for transmission to suitable receiver
apparatus for execution by a data processing apparatus. A
computer-storage medium can be, or be included in, a
computer-readable storage device, a computer-readable storage
substrate, a random or serial-access memory array or device, or a
combination thereof. Moreover, while a computer-storage medium is
not a propagated signal, a computer-storage medium may be a source
or destination of computer-program instructions encoded in an
artificially-generated propagated signal. The computer-storage
medium can also be, or be included in, one or more separate
physical components or media (e.g., multiple CDs, disks, or other
storage devices). Additionally, the operations described in this
specification may be implemented as operations performed by a
data-processing apparatus on data stored on one or more
computer-readable storage devices or received from other
sources.
[0260] While this specification may include many specific
implementation details, the implementation details should not be
construed as limitations on the scope of any claimed subject
matter, but rather be construed as descriptions of features
specific to particular embodiments. Certain features that are
described in this specification in the context of separate
embodiments may also be implemented in combination in a single
embodiment. Conversely, various features that are described in the
context of a single embodiment may also be implemented in multiple
embodiments separately or in any suitable subcombination. Moreover,
although features may be described above as acting in certain
combinations and even initially claimed as such, one or more
features from a claimed combination may in some cases be excised
from the combination, and the claimed combination may be directed
to a subcombination or variation of a subcombination.
[0261] Similarly, while operations are depicted in the drawings in
a particular order, this should not be understood as requiring that
such operations be performed in the particular order shown or in
sequential order, or that all illustrated operations be performed,
to achieve desirable results. In certain circumstances,
multitasking and parallel processing may be advantageous. Moreover,
the separation of various system components in the embodiments
described above should not be understood as requiring such
separation in all embodiments, and it should be understood that the
described program components and systems can generally be
integrated together in a single software product or packaged into
multiple software products.
[0262] Thus, particular embodiments of the subject matter have been
described herein. Other embodiments are within the scope of the
following claims. In some cases, the actions set forth in the
claims may be performed in a different order and still achieve
desirable results. Additionally, the processes depicted in the
accompanying figures do not necessarily require the particular
order shown, or sequential order, to achieve desirable results. In
certain implementations, multitasking and parallel processing may
be advantageous.
[0263] As will be recognized by those skilled in the art, the
innovative concepts described herein may be modified and varied
over a wide range of applications. Accordingly, the scope of
claimed subject matter should not be limited to any of the specific
exemplary teachings discussed above, but is instead defined by the
following claims.
* * * * *